View source for Essential oil

{{Short description|Hydrophobic liquid containing volatile aroma compounds from plants}}
{{cs1 config|name-list-style=vanc}}
{{Hatnote group|
{{For|the Midnight Oil album|Essential Oils (album)}}
{{Distinguish|essential fatty acid|fragrance oils}}
}}
{{Vegetable oils|image=SandalwoodEssOil.png|caption=[[Sandalwood oil]]}}

An '''essential oil''' is a concentrated [[hydrophobic]] liquid containing [[Volatility (chemistry)|volatile]] (easily evaporated at normal temperatures) [[chemical compound]]s from [[plant]]s. Essential oils are also known as '''volatile oils''', '''ethereal oils''', '''aetheroleum''', or simply as the oil of the plant from which they were extracted, such as [[oil of clove]]. An essential [[oil]] is essential in the sense that it contains the essence of the plant's [[fragrance]]—the characteristic fragrance of the plant from which it is derived.<ref>{{cite book |chapter= essential oil |title= Oxford English Dictionary |edition= online, American English |chapter-url= http://www.oxforddictionaries.com/us/definition/american_english/essential-oil?q=essential+oil |access-date= 2014-07-21  |archive-url= https://web.archive.org/web/20140809030553/http://www.oxforddictionaries.com/us/definition/american_english/essential-oil?q=essential+oil |archive-date= 2014-08-09 }}</ref> The term "essential" used here does ''not'' mean required or usable by the human body, as with the terms [[essential amino acid]] or [[essential fatty acid]], which are so called because they are nutritionally required by a living organism.<ref>{{cite journal |pmid=10867060 |year=2000 |last1=Reeds |first1=P. J. |title=Dispensable and indispensable amino acids for humans |journal=The Journal of Nutrition |volume=130 |issue=7 |pages=1835S–40S |doi=10.1093/jn/130.7.1835S |doi-access=free }}</ref>

Essential oils are generally extracted by [[distillation]], often [[steam distillation|by using steam]]. Other processes include [[Ram press (food)|expression]], [[Liquid-liquid extraction|solvent extraction]], ''[[sfumatura]]'', [[Absolute (perfumery)|absolute]] oil extraction, resin tapping, wax embedding, and cold pressing. They are used in [[perfumes]], [[cosmetics]], [[soap]]s, [[Air freshener|air fresheners]] and other products, for [[flavoring]] food and drink, and for adding scents to [[incense]] and household cleaning products.

Essential oils are often used for [[aromatherapy]], a form of [[alternative medicine]] in which healing effects are ascribed to aromatic compounds. Aromatherapy may be useful to induce relaxation, but there is not sufficient evidence that it can effectively treat any condition.<ref name="lee">{{cite journal|last1=Lee|first1=Myeong Soo|last2=Choi|first2=Jiae Choi|title=Aromatherapy for health care: an overview of systematic reviews|journal=Maturitas|date=2012|volume=3|issue=71|pages=257–260|doi=10.1016/j.maturitas.2011.12.018|pmid=22285469}}</ref> Improper use of essential oils may cause harm including allergic reactions, inflammation and skin irritation.  Children may be particularly susceptible to the toxic effects of improper use.<ref name="ReferenceE">{{cite journal |doi=10.3233/JRS-2012-0568 |pmid=22936057 |year=2012 |last1=Posadzki |first1=P |title=Adverse effects of aromatherapy: A systematic review of case reports and case series |journal=The International Journal of Risk & Safety in Medicine |volume=24 |issue=3 |pages=147–61 |last2=Alotaibi |first2=A |last3=Ernst |first3=E }}</ref><ref name="poison.org">{{Cite web|title=Essential oils: Poisonous when misused|url=https://www.poison.org/articles/2014-jun/essential-oils|publisher=US National Capital Poison Center|language=en|access-date=2017-12-01}}</ref> Essential oils can be poisonous if ingested or absorbed through the skin.<ref name=poison.org/>

==Production==
{{main|Extraction (fragrance)}}

===Distillation===
{{see also|Distillation}}
{{references|section|date=November 2022}}

Most common essential oils such as [[Lavandula|lavender]], [[peppermint]], [[tea tree oil]], [[patchouli]], and [[eucalyptus oil|eucalyptus]] are distilled. Raw plant material, consisting of the [[flower]]s, [[leaf|leaves]], [[wood]], [[Bark (botany)|bark]], [[root]]s, [[seed]]s, or [[peel (fruit)|peel]], is put into an [[alembic]] (distillation apparatus) over water. As the water is heated, the steam passes through the plant material, vaporizing the volatile compounds. The vapors flow through a coil, where they condense back to liquid, which is then collected in the receiving vessel.

Most oils are distilled in a single process. One exception is ''ylang-ylang'' (''[[Cananga odorata]]'') which is purified through a [[fractional distillation]].

The recondensed water is referred to as a hydrosol, hydrolat, [[herbal distillate]], or plant water essence, which may be sold as another fragrant product. Hydrosols include [[rose water]], [[lavender]] water, [[lemon balm]], [[clary sage]], and [[orange blossom water]].

===Expression===
Most [[citrus]] peel oils are expressed mechanically or cold-pressed (similar to [[olive oil extraction]]).<ref>{{cite web|title=How Are Essential Oils Extracted?|url=https://naha.org/explore-aromatherapy/about-aromatherapy/how-are-essential-oils-extracted/|last1=Shutes|first1=Jade|website=NAHA – National Association for Holistic Aromatherapy|archive-url=https://web.archive.org/web/20130611075007/https://naha.org/explore-aromatherapy/about-aromatherapy/how-are-essential-oils-extracted/|archive-date=11 June 2013|access-date=16 June 2019}}</ref> Due to the relatively large quantities of oil in citrus peel and low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils are obtained as [[byproduct]]s of the citrus industry.

Before the discovery of distillation, all essential oils were extracted by pressing.<ref>{{Cite book|title = The Aromatherapy Handbook: The Secret Healing Power Of Essential Oils|last = Ryman|first = Daniele|publisher = Century Publishing CO. Ltd.|year = 1984|isbn = 978-0-85207-215-8|pages = Chapter 3}}</ref>

===Solvent extraction===
Most flowers contain too little volatile oil to undergo expression, but their chemical components are too delicate and easily denatured by the high heat used in steam distillation. Instead, a [[solvent]] such as [[hexane]] or [[supercritical carbon dioxide]] is used to extract the oils.<ref>{{Cite journal|last1=Aizpurua-Olaizola|first1=Oier|last2=Ormazabal|first2=Markel|last3=Vallejo|first3=Asier|last4=Olivares|first4=Maitane|last5=Navarro|first5=Patricia|last6=Etxebarria|first6=Nestor|last7=Usobiaga|first7=Aresatz|date=2015-01-01|title=Optimization of supercritical fluid consecutive extractions of fatty acids and polyphenols from Vitis vinifera grape wastes|journal=Journal of Food Science|volume=80|issue=1|pages=E101–107|doi=10.1111/1750-3841.12715|issn=1750-3841|pmid=25471637}}</ref> Extracts from [[hexane]] and other hydrophobic solvents are called ''[[Concrete (perfumery)|concretes]]'', which are a mixture of essential oil, [[wax]]es, [[resin]]s, and other [[lipophilic]] (oil-soluble) plant material.

Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. Often, another solvent, such as [[ethanol|ethyl alcohol]], is used to extract the fragrant oil from the concrete. The alcohol solution is chilled to {{convert|-18|C|F}} for more than 48 hours which causes the [[wax]]es and [[lipid]]s to precipitate out. The precipitates are then filtered out and the ethanol is removed from the remaining solution by evaporation, vacuum purge, or both, leaving behind the ''[[Absolute (fragrance)|absolute]]''.

Supercritical carbon dioxide is used as a solvent in [[supercritical fluid]] extraction. This method can avoid [[petrochemical]] residues in the product and the loss of some "top notes" when steam distillation is used. It does not yield an absolute directly. The supercritical carbon dioxide will extract both the waxes and the essential oils that make up the concrete.  Subsequent processing with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction temperature, will separate the waxes from the essential oils.  This lower temperature process prevents the decomposition and denaturing of compounds. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts to a gas, leaving no residue.

===Production quantities===

Estimates of total production of essential oils are difficult to obtain. One estimate, compiled from data in 1989, 1990, and 1994 from various sources, gives the following total production, in tonnes, of essential oils for which more than 1,000 tonnes were produced.<ref>{{cite web |url= http://isotc.iso.org/livelink/livelink/971087/ISO_TC_054__Essential_oils_.pdf |title= ISO TC 54 Business Plan – Essential oils | access-date= 2006-09-14}} It is unclear from the source what period of time the quoted figures include.</ref>

:{| class="wikitable"
! Oil !! Tonnes
|-
| [[Orange (fruit)|Sweet orange]] || style="text-align:right;"| 12,000
|-
| ''[[Mentha arvensis]]'' || style="text-align:right;"| 4,800
|-
| [[Peppermint]] || style="text-align:right;"| 3,200
|-
| [[Cedrus|Cedar]]wood || style="text-align:right;"| 2,600
|-
| [[Lemon]] || style="text-align:right;"| 2,300
|-
| ''[[Eucalyptus globulus]]'' || style="text-align:right;"| 2,070
|-
| ''[[Litsea cubeba]]'' || style="text-align:right;"| 2,000
|-
| [[Clove]] (leaf) || style="text-align:right;"| 2,000
|-
| [[Spearmint]] || style="text-align:right;"| 1,300
|}

==Uses and cautions==
{{More medical citations needed|section|date=September 2010}}

Taken by mouth, many essential oils can be dangerous in high concentrations. Typical effects begin with a burning feeling, followed by salivation.<ref name=Sapeika>{{cite book |last= Sapeika |first= Norman |title= Actions and Uses of Drugs |publisher= A.A. Balkema |year= 1963}}{{page needed|date= October 2014}}</ref> Different essential oils may have drastically different pharmacology. Some act as local anesthetic [[counterirritant]]s and, thereby, exert an [[antitussive]] (cough suppressing) effect.<ref name=Sapeika/><ref name="Turpentine">{{citation|last=Haneke|first=Karen E|title=Turpentine (Turpentine Oil, Wood Turpentine, Sulfate Turpentine, Sulfite Turpentine) [8006-64-2]: Review of Toxicological Literature|date=February 2002|url=http://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/turpentine_508.pdf|issue=Contract No. N01–ES–65402|publisher=[[National Institute of Environmental Health Sciences]]}}{{page needed|date=October 2014}}</ref> Many essential oils, particularly [[tea tree oil]], may cause [[contact dermatitis]].<ref>{{cite journal |doi=10.1097/DER.0b013e31823e202d |pmid=22653070 |title=Tea Tree Oil |journal=Dermatitis |volume=23 |issue=1 |pages=48–9 |year=2012 |last1=Larson |first1=David |last2=Jacob |first2=Sharon E. }}</ref><ref name="ReferenceA">{{cite journal |doi=10.1111/j.1600-0536.2007.01275.x |pmid=18416758 |title=Occupational contact dermatitis due to essential oils |journal=Contact Dermatitis |volume=58 |issue=5 |pages=282–4 |year=2008 |last1=Trattner |first1=Akiva |last2=David |first2=Michael |last3=Lazarov |first3=Aneta |s2cid=10674102 }}</ref><ref name="ReferenceB">{{cite journal |doi=10.1046/j.1440-0960.2002.00598.x |pmid=12121401 |title=Allergic contact dermatitis following exposure to essential oils |journal=Australasian Journal of Dermatology |volume=43 |issue=3 |pages=211–3 |year=2002 |last1=Bleasel |first1=Narelle |last2=Tate |first2=Bruce |last3=Rademaker |first3=Marius |s2cid=46674505 }}</ref><ref name="ReferenceC">{{cite journal |doi=10.1034/j.1600-0536.2000.043001041.x |pmid=10902588 |title=Short Communications |journal=Contact Dermatitis |volume=43 |issue=1 |pages=41–2 |year=2000 |last1=Isaksson |first1=M |last2=Brandão |first2=F. M. |last3=Bruze |first3=M |last4=Goossens |first4=A |s2cid=221576846 }}</ref> Menthol and some others produce a feeling of cold followed by a sense of burning.

In Australia essential oils (mainly eucalyptus) have been increasingly causing cases of poisoning, mostly of children. In the period 2014–2018, there were 4,412 poisoning incidents reported in [[New South Wales]].<ref name=leeka>{{cite journal |vauthors=Lee KA, Harnett JE, Cairns R|title=Essential oil exposures in Australia: analysis of cases reported to the NSW Poisons Information Centre |journal=Medical Journal of Australia |year=2019 |volume=212 |issue=3 |pages=132–133 |issn=0025-729X |doi=10.5694/mja2.50403 |pmid=31709543 |s2cid=207940224 |doi-access=free }}
*{{lay source |template = cite news|url = https://sydney.edu.au/news-opinion/news/2019/12/09/essential-oil-poisoning-calls-on-the-rise-children-most-affected.html||title = Essential oil poisoning calls on the rise, children most affected |date= December 9, 2019 |website= University of Sydney}}</ref>

==Use in aromatherapy==
{{main|Aromatherapy}}
[[File:Reed diffuser.jpg|thumb|Essential oils can be used in aromatherapy by using essential oil diffusers.<ref name=simplerandsmarter>{{Cite web|title=Aromatherapy: The Best Essential Oil Diffuser|url=https://simplerandsmarter.com.au/best-essential-oil-diffuser/|website=simplerandsmarter.com.au|language=en|access-date=2016-05-15}}</ref>]]
Aromatherapy is a form of [[alternative medicine]] in which healing effects are ascribed to the aromatic compounds in essential oils and other plant extracts. Aromatherapy may be useful to induce relaxation, but there is not sufficient evidence that essential oils can effectively treat any condition.<ref name=lee/> Scientific research indicates that essential oils cannot treat or cure any chronic disease or other illnesses.<ref name=lee/> Much of the research on the use of essential oils for health purposes has serious methodological errors. In a systemic review of 201 published studies on essential oils as alternative medicines, only 10 were found to be of acceptable methodological quality, and even these 10 were still weak in reference to scientific standards.<ref name=lee/> Use of essential oils may cause harm including allergic reactions and skin irritation; After receiving a facial at an all-natural salon, a person experienced severe skin irritation, which highlighted the potential dangers of using "clean" beauty products marketed as being made from natural ingredients. This incident underscores the misconception that natural compounds are always safe, revealing a growing awareness within the beauty industry about the risks associated with essential oils, which can lead to allergic reactions and skin damage;<ref>{{Cite news |last=Schiffer |first=Jessica |date=March 11, 2021 |title=Essential Oils May Be Wreaking Havoc on Your Skin |url=https://www.nytimes.com/2021/03/11/style/self-care-essential-oils-may-be-wreaking-havoc-on-your-skin.html |work=The New York Times}}</ref> there has been at least one case of death.<ref name="ReferenceE"/>

== Use as pesticide ==

Research has shown that some essential oils have potential as a natural [[pesticide]]. In case studies, certain oils have been shown to have a variety of deterring effects on pests, specifically insects and select arthropods.<ref name=":0">{{Cite journal|date=2010-01-01|title=Repellent activity of essential oils: A review|journal=Bioresource Technology|language=en|volume=101|issue=1|pages=372–378|doi=10.1016/j.biortech.2009.07.048|pmid=19729299|issn=0960-8524|last1=Nerio|first1=Luz Stella|last2=Olivero-Verbel|first2=Jesus|last3=Stashenko|first3=Elena|bibcode=2010BiTec.101..372N }}</ref> These effects may include repelling, inhibiting digestion, stunting growth,<ref name="Regnault-Roger-et-al-2012">{{cite journal | last1=Regnault-Roger | first1=Catherine | last2=Vincent | first2=Charles | last3=Arnason | first3=John Thor | title=Essential Oils in Insect Control: Low-Risk Products in a High-Stakes World | journal=[[Annual Review of Entomology]] | volume=57 | issue=1 | date=2012-01-07 | issn=0066-4170 | doi=10.1146/annurev-ento-120710-100554 | pages=405–424 | pmid=21942843}}</ref> decreasing rate of reproduction, or death of pests that consume the oil. However, the molecules within the oils that cause these effects are normally non-toxic for mammals. These specific actions of the molecules allow for widespread use of these "green" pesticides without harmful effects to anything else other than pests.<ref name=":3">{{Cite journal|last=Regnault-Roger|first=Catherine|s2cid=39007186|date=1997-02-01|title=The potential of botanical essential oils for insect pest control|journal=Integrated Pest Management Reviews|language=en|volume=2|issue=1|pages=25–34|doi=10.1023/A:1018472227889|issn=1353-5226}}</ref> Essential oils that have been investigated include rose, lemon grass, lavender, thyme, peppermint, basil, cedarwood, and eucalyptus.<ref name="Koul-et-al-2008">{{cite journal | last1=Koul | first1=Opender | last2=Suresh | first2=Walia | first3=G. S. | last3=Dhaliwal | title=Essential Oils as Green Pesticides: Potential and Constraints |url=https://www.researchgate.net/publication/270157815 | journal=Biopesticides International | volume=4 | issue=1 | date=2008 | pages=63–84 | s2cid=85741148}}</ref>

Although they may not be the perfect replacement for all synthetic pesticides, essential oils have prospects for crop or indoor plant protection, urban pest control,<ref>{{Cite journal|date=2000-09-12|title=Plant essential oils for pest and disease management|journal=Crop Protection|language=en|volume=19|issue=8–10|pages=603–608|doi=10.1016/S0261-2194(00)00079-X|issn=0261-2194|last1=Isman|first1=Murray B|bibcode=2000CrPro..19..603I |s2cid=39469817 }}</ref> and marketed insect repellents, such as bug spray. Certain essential oils have been shown in studies to be comparable, if not exceeding, in effectiveness to [[DEET]], which is currently marketed as the most effective mosquito repellent. Although essential oils are effective as pesticides when first applied in uses such as mosquito repellent applied to the skin, it is only effective in the vapor stage. Since this stage is relatively short-lived, creams and polymer mixtures are used in order to elongate the vapor period of effective repellency.<ref name=":0" />

In any form, using essential oils as green pesticides rather than synthetic pesticides has ecological benefits such as decreased residual actions.<ref name="Koul-et-al-2008" /> In addition, increased use of essential oils as pest control could have not only ecological, but economical benefits as the essential oil market diversifies<ref name=":3" /> and popularity increases among organic farmers and environmentally conscious consumers.<ref name="Regnault-Roger-et-al-2012" /> {{As of|2012}} some EOs are authorized, and in use, in the [[European Union]]: ''[[Melaleuca]]'' oil as a [[fungicide]], [[citronella oil]] as a [[herbicide]], ''[[Syzygium aromaticum]]'' oil as a fungicide and bactericide, ''[[Mentha spicata]]'' oil as a [[plant growth regulator]]; ''[[Citrus sinensis]]'' oil (only in France) for ''[[Bemisia tabaci]]'' on ''[[Cucurbita pepo]]'' and ''[[Trialeurodes vaporariorum]]'' on ''[[Solanum lycopersicum]]''; and approvals for oils of ''[[Thymus (plant)|Thymus]]'', ''C. sinensis'', and ''[[Tagetes]]'' as insecticides are pending.<ref name="Regnault-Roger-et-al-2012" />

== Use in food ==
{{Globalize|date=June 2024}}
In relation with their food applications, although these oils have been used throughout history as food preservatives, it was in the 20th century when essential oils were considered as [[Generally recognized as safe|Generally Recognized as Safe]] (GRAS) by the United States’ [[Food and Drug Administration]] (FDA).<ref>{{Cite book|title=Essential oils in food preservation, flavor and safety|vauthors =Preedy VR|isbn=978-0-12-416644-8|location=Amsterdam|oclc=922581414|date = 2015-09-28}}</ref>

'''GRAS substances according to the FDA<ref name="US FDA" />'''
{| class="wikitable"
!Common name
!Botanical name of plant source
|-
|[[Alfalfa]]
|''Medicago sativa'' L.
|-
|[[Allspice]]
|''Pimenta officinalis'' Lindl.
|-
|[[Bitter almond]], free from cyanide<ref>{{cite web | url=https://www.spektrum.de/quiz/wieviel-prozent-blausaeure-enthaelt-natuerliches-bittermandeloel/594066 | title=Wieviel Prozent Blausäure enthält natürliches Bittermandelöl? }}</ref>
|''Prunus amygdalus'' Batsch, ''Prunus armeniaca'' L., or ''Prunus persica'' (L.) Batsch.
|-
|[[Ambrette]] (seed)
|Hibiscus moschatus Moench.
|-
|[[Angelica archangelica|Angelica root]]
|rowspan=3|''Angelica archangelica'' L.
|-
|[[Angelica archangelica|Angelica seed]]
|-
|[[Angelica archangelica|Angelica stem]]
|-
|[[Angostura trifoliata|Angostura]] ([[cusparia]] bark)
|''Galipea officinalis'' Hancock, ''Angostura trifoliata''
|-
|[[Anise]]
|''Pimpinella anisum'' L.
|-
|[[Asafetida]]
|''Ferula assa-foetida'' L. and related spp. of ''Ferula''
|-
|Balm ([[lemon balm]])
|''Melissa officinalis'' L.
|-
|[[Balsam of Peru]]
|''Myroxylon pereirae'' Klotzsch.
|-
|[[Basil]]
|''Ocimum basilicum'' L.
|-
|[[Bay leaves]]
|''Laurus nobilis'' L.
|-
|[[Pimenta racemosa|Bay (myrcia oil)]]
|''Pimenta racemosa'' (Mill.) J. W. Moore.
|-
|[[Bergamot orange|Bergamot]] (bergamot orange)
|''Citrus aurantium'' L. subsp. ''bergamia'' Wright et Arn.
|-
|[[Bitter almond]] (free from prussic acid)
|''Prunus amygdalus'' Batsch, ''Prunus armeniaca'' L., or ''Prunus persica'' (L.) Batsch.
|-
|[[Rosewood oil|Bois de rose]]
|''Aniba rosaeodora'' Ducke.
|-
|[[Theobroma cacao|Cacao]]
|''Theobroma cacao'' L.
|-
|[[Matricaria chamomilla|Camomile (chamomile) flowers]], German or Hungarian
|''Matricaria chamomilla'' L.
|-
|[[Chamaemelum nobile|Camomile (chamomile) flowers]], Roman or English
|''Anthemis nobilis'' L.
|-
|[[Cananga odorata|Cananga]]
|''Cananga odorata'' Hook. f. and Thoms.
|-
|[[Capsicum]]
|''Capsicum frutescens'' L. and ''Capsicum annuum'' L.
|-
|[[Caraway]]
|''Carum carvi'' L.
|-
|[[Cardamom|Cardamom seed]] (cardamon)
|''Elettaria cardamomum'' Maton.
|-
|[[Carob bean]]
|''Ceratonia siliqua'' L.
|-
|[[Carrot]]
|''Daucus carota'' L.
|-
|[[Croton eluteria|Cascarilla bark]]
|''Croton eluteria'' Benn.
|-
|[[Cinnamomum cassia|Cassia bark, Chinese]]
|''Cinnamomum cassia'' Blume.
|-
|[[Cinnamomum burmannii|Cassia bark, Padang or Batavia]]
|''Cinnamomum burmanni'' Blume.
|-
|[[Saigon cinnamon|Cassia bark, Saigon]]
|''Cinnamomum loureirii'' Nees.
|-
|[[Celery seed]]
|''Apium graveolens'' L.
|-
|[[Prunus serotina|Cherry, wild]], bark
|''Prunus serotina'' Ehrh.
|-
|[[Chervil]]
|''Anthriscus cerefolium'' (L.) Hoffm.
|-
|[[Chicory]]
|''Cichorium intybus'' L.
|-
|[[Cinnamomum verum|Cinnamon bark, Ceylon]]
|''Cinnamomum zeylanicum'' Nees.
|-
|[[Cinnamomum cassia|Cinnamon bark, Chinese]]
|''Cinnamomum cassia'' Blume.
|-
|[[Saigon cinnamon|Cinnamon bark, Saigon]]
|''Cinnamomum loureirii'' Nees.
|-
|[[Cinnamomum verum|Cinnamon leaf, Ceylon]]
|''Cinnamomum zeylanicum'' Nees.
|-
|[[Cinnamon leaf oil|Cinnamon leaf]], Chinese
|''Cinnamomum cassia'' Blume.
|-
|[[Cinnamon leaf oil|Cinnamon leaf]], Saigon
|''Cinnamomum loureirii'' Nees.
|-
|[[Citronella oil|Citronella]]
|''Cymbopogon nardus'' Rendle.
|-
|[[Citrus|Citrus peels]]
|''Citrus'' spp.
|-
|[[Clary Sage|Clary]] (clary sage)
|''Salvia sclarea'' L.
|-
|[[Clover]]
|''Trifolium'' spp.
|-
|[[Coca]] (decocainized)
|''Erythroxylum coca'' Lam. and other spp. of ''Erythroxylum''
|-
|[[Coffea|Coffee]]
|''Coffea'' spp.
|-
|[[Kola nut|Cola nut]]
|''Cola acuminata'' Schott and Endl., and other spp. of ''Cola''
|-
|[[Coriander]]
|''Coriandrum sativum'' L.
|-
|[[Cumin]] (cummin)
|''Cuminum cyminum'' L.
|-
|[[Bitter orange|Curaçao orange peel]] (orange, bitter peel)
|''Citrus aurantium'' L.
|-
|[[Angostura (plant)|Cusparia]] bark
|''Galipea officinalis'' Hancock
|-
|[[Dandelion]]
|rowspan=2|''Taraxacum officinale'' Weber and ''Taraxacum laevigatum'' DC.
|-
|Dandelion root
|-
|Dog grass (quackgrass, triticum)
|''Agropyron repens'' (L.) Beauv.
|-
|Elder flowers
|''Sambucus canadensis'' L. and ''Sambucus nigra'' I.
|-
|[[Estragole]] (esdragol, esdragon, tarragon)
|rowspan=2|''Artemisia dracunculus'' L.
|-
|[[Estragole|Estragon (tarragon)]]
|-
|[[Fennel]], sweet
|''Foeniculum vulgare'' Mill.
|-
|[[Fenugreek]]
|''Trigonella foenum-graecum'' L.
|-
|[[Galangal|Galanga]] (galangal)
|''Alpinia officinarum'' Hance.
|-
|[[Geranium]]
|''Pelargonium'' spp.
|-
|Geranium, East Indian
|''Cymbopogon martini'' Stapf.
|-
|Geranium, rose
|''Pelargonium graveolens'' L'Her.
|-
|[[Ginger]]
|''Zingiber officinale'' Rosc.
|-
|[[Grapefruit]]
|''Citrus paradisi'' Macf.
|-
|[[Guava]]
|''Psidium'' spp.
|-
|[[Hickory]] bark
|''Carya'' spp.
|-
|Horehound (hoarhound)
|''Marrubium vulgare'' L.
|-
|[[Hops]]
|''Humulus lupulus'' L.
|-
|[[Horsemint]]
|''Monarda punctata'' L.
|-
|[[Hyssopus officinalis|Hyssop]]
|''Hyssopus officinalis'' L.
|-
|[[Helichrysum|Immortelle]]
|''Helichrysum augustifolium'' DC.
|-
|[[Jasmine]]
|''Jasminum officinale'' L. and other spp. of ''Jasminum''
|-
|[[Juniper]] (berries)
|''Juniperus communis'' L.
|-
|[[Kola nut]]
|''Cola acuminata'' Schott and Endl., and other spp. of ''Cola''
|-
|Laurel berries
|''Laurus nobilis'' L.
|-
|Laurel leaves
|''Laurus'' spp.
|-
|[[Lavender]]
|''Lavandula officinalis'' Chaix
|-
|Lavender, spike
|''Lavandula latifolia'' Vill.
|-
|[[Lavandin]]
|Hybrids between ''Lavandula officinalis'' Chaix and ''Lavandula latifolin'' Vill.
|-
|[[Lemon]]
|''Citrus limon'' (L.) Burm. f.
|-
|Lemon balm (see balm)
|''Melissa officinalis'' L.
|-
|[[Cymbopogon|Lemongrass]]
|''Cymbopogon citratus'' DC. and ''Cymbopogon lexuosus'' Stapf.
|-
|Lemon peel
|''Citrus limon'' (L.) Burm. f.
|-
|[[Lime (fruit)|Lime]]
|''Citrus aurantifolia'' Swingle.
|-
|[[Tilia cordata|Linden]] flowers
|''Tilia'' spp.
|-
|[[Locust bean]]
|''Ceratonia siliqua'' L,
|-
|[[Lupulin]]
|''Humulus lupulus'' L.
|-
|[[Mace (spice)|Mace]]
|''Myristica fragrans'' Houtt.
|-
|Mandarin
|''Citrus reticulata'' Blanco.
|-
|[[Marjoram]], sweet
|''Majorana hortensis'' Moench.
|-
|[[Yerba mate|Mate, yerba]]
|''Ilex paraguariensis'' St. Hil.
|-
|Melissa (see balm)
|
|-
|[[Menthol]]
|rowspan=2|''Mentha'' spp.
|-
|[[Menthyl acetate]]
|-
|[[Molasses]] (extract)
|''Saccharum officinarum'' L.
|-
|[[Mustard (condiment)|Mustard]]
|''Brassica'' spp.
|-
|[[Naringin]]
|''Citrus paradisi'' Macf.
|-
|[[Neroli|Neroli, bigarade]]
|''Citrus aurantium'' L.
|-
|[[Nutmeg]]
|''Myristica fragrans'' Houtt.
|-
|[[Onion]]
|''Allium cepa'' L.
|-
|Orange, bitter, flowers
|rowspan=2|''Citrus aurantium'' L.
|-
|Orange, bitter, peel
|-
|Orange leaf
|rowspan=4|''Citrus sinensis'' (L.) Osbeck.
|-
|Orange, sweet
|-
|Orange, sweet, flowers
|-
|Orange, sweet, peel
|-
|[[Origanum]]
|''Origanum'' spp.
|-
|[[Cymbopogon martinii|Palmarosa]]
|''Cymbopogon martini'' Stapf.
|-
|[[Paprika]]
|''Capsicum annuum'' L.
|-
|[[Parsley]]
|''Petroselinum crispum'' (Mill.) Mansf.
|-
|[[Black pepper|Pepper, black]]
|rowspan=2|''Piper nigrum'' L.
|-
|Pepper, white
|-
|[[Peppermint]]
|''Mentha piperita'' L.
|-
|[[Balsam of Peru|Peruvian balsam]]
|''Myroxylon pereirae'' Klotzsch.
|-
|[[Petitgrain]]
|''Citrus aurantium'' L.
|-
|Petitgrain lemon
|''Citrus limon'' (L.) Burm. f.
|-
|Petitgrain mandarin or tangerine
|''Citrus reticulata'' Blanco.
|-
|[[Allspice|Pimenta]]
|rowspan=2|''Pimenta officinalis'' Lindl.
|-
|[[Pimenta (genus)|Pimenta leaf]]
|-
|[[Chimaphila umbellata|Pipsissewa leaves]]
|''Chimaphila umbellata'' Nutt.
|-
|[[Pomegranate]]
|''Punica granatum'' L.
|-
|[[Zanthoxylum|Prickly ash bark]]
|''Xanthoxylum'' (or ''Zanthoxylum'') ''americanum'' Mill. or ''Xanthoxylum clava-herculis'' L.
|-
|[[Rose]] absolute
|rowspan=5|''Rosa alba'' L., ''Rosa centifolia'' L., ''Rosa damascena'' Mill., ''Rosa gallica'' L., and vars. of these spp.
|-
|Rose (otto of roses, attar of roses)
|-
|Rose buds
|-
|Rose flowers
|-
|Rose fruit (hips)
|-
|Rose geranium
|''Pelargonium graveolens'' L'Her.
|-
|Rose leaves
|''Rosa'' spp.
|-
|[[Rosemary]]
|''Rosmarinus officinalis'' L.
|-
|[[Saffron]]
|''Crocus sativus'' L.
|-
|[[Sage (herb)|Sage]]
|''Salvia officinalis'' L.
|-
|[[Salvia triloba|Sage]], Greek
|''Salvia triloba'' L.
|-
|[[ Salvia officinalis subsp. lavandulifolia|Sage, Spanish]]
|''Salvia officinalis'' subsp. ''lavandulifolia'' (Vahl) Gams
|-
|[[Carob|St. John's bread]]
|''Ceratonia siliqua'' L.
|-
|[[Summer savory|Savory, summer]]
|''Satureia hortensis'' L.
|-
|[[Winter savory|Savory]], winter
|''Satureia montana'' L.
|-
|''[[Schinus molle]]''
|''Schinus molle'' L.
|-
|[[Prunus spinosa|Sloe berries]] (blackthorn berries)
|''Prunus spinosa'' L.
|-
|[[Spearmint]]
|''Mentha spicata'' L.
|-
|[[Spike lavender]]
|''Lavandula latifolia'' Vill.
|-
|[[Tamarind]]
|''Tamarindus indica'' L.
|-
|[[Tangerine]]
|''Citrus reticulata'' Blanco.
|-
|[[Tarragon]]
|''Artemisia dracunculus'' L.
|-
|[[Camellia sinensis|Tea]]
|''Thea sinensis'' L.
|-
|[[Thymelaeaceae|Thyme]]
|rowspan=2|''Thymus vulgaris'' L. and ''Thymus zygis'' var. ''gracilis'' Boiss.
|-
|[[Thyme]], white
|-
|[[Thymus serpyllum|Thyme]], wild or creeping
|''Thymus serpyllum'' L.
|-
|[[Elymus repens|Triticum]] (see dog grass)
|''Elymus repens''
|-
|[[Agave amica|Tuberose]]
|''Polianthes tuberosa'' L.
|-
|[[Turmeric]]
|''Curcuma longa'' L.
|-
|[[Vanilla]]
|''Vanilla planifolia'' Andr. or ''Vanilla tahitensis'' J. W. Moore.
|-
|[[Viola (plant)|Violet flowers]]
|rowspan=3|''Viola odorata'' L.
|-
|[[Viola odorata|Violet leaves]]
|-
|[[Viola odorata|Violet leaves absolute]]
|-
|[[Prunus serotina|Wild cherry bark]]
|''Prunus serotina'' Ehrh.
|-
|[[Cananga odorata|Ylang-ylang]]
|''Cananga odorata'' Hook. f. and Thoms.
|-
|[[Curcuma zedoaria|Zedoary bark]]
|''Curcuma zedoaria'' Rosc.
|}

===As antimicrobials===
The most commonly used essential oils with antimicrobial action are: [[β-caryophyllene]], [[eugenol]], [[eugenol acetate]], [[carvacrol]], [[linalool]], [[thymol]], [[geraniol]], [[geranyl acetate]], [[bicyclogermacrene]], [[cinnamaldehyde]], [[geranial]], [[neral (citral)|neral]], [[1,8-Cineole|1,8-cineole]], [[methyl chavicol]], [[methyl cinnamate]], [[methyl eugenol]], [[camphor]], [[α-thujone]], [[viridiflorol]], [[limonene]], [[(Z)-linalool oxide|(''Z'')-linalool oxide]], [[α-pinene]], [[p-cymene|''p''-cymene]], [[(E)-caryophyllene|(''E'')-caryophyllene]], [[γ-terpinene]].<ref name="Rao-et-al-2019" /><ref>{{cite journal | last=Graikou | first=K. | last2=Gortzi | first2=O. | last3=Mantanis | first3=G. | author3-link=George Mantanis | last4=Chinou | first4=I. | title=Chemical composition and biological activity of the essential oils from the wood of Pinus heldreichii Christ. var. leucodermis | journal=European Journal of Wood and Wood Products | volume=70 | issue=5 | date=2012 | issn=0018-3768 | doi=10.1007/s00107-012-0596-9 | pages=615–620}}</ref>

Some essential oils are effective [[antimicrobials]] and have been evaluated for food incorporation [[in vitro]]. However, actual deployment is rare because much higher concentrations are required in real foods. Some or all of this lower effectiveness is due to large differences between [[culture medium]] and foods in chemistry (especially lipid content), viscosity, and duration of inoculation/storage.<ref name="Rao-et-al-2019">{{cite journal | last1=Rao | first1=Jiajia | last2=Chen | first2=Bingcan | last3=McClements | first3=David Julian | author3-link=David J. McClements | title=Improving the Efficacy of Essential Oils as Antimicrobials in Foods: Mechanisms of Action | journal=[[Annual Review of Food Science and Technology]]  | volume=10 | issue=1 | date=2019-03-25 | issn=1941-1413 | doi=10.1146/annurev-food-032818-121727 | pages=365–387| pmid=30653350 | s2cid=58656780 | doi-access=free }}</ref>

==Dilution==

Essential oils are usually [[lipophilic]] (literally: ''"oil-loving"'') compounds that are immiscible (not [[miscible]]) with water. They can be diluted in [[solvent]]s like pure [[ethanol]] and [[polyethylene glycol]].{{citation needed|date=May 2021}}

==Raw materials==<!-- This section is linked from [[Vegetable fats and oils]] -->
{{main|List of essential oils}}

Essential oils are derived from sections of plants. Some plants, like the [[bitter orange]], are sources of several types of essential oil.

:{| class="wikitable" |
| valign="top" |
;[[Bark (botany)|Bark]]
* [[Cinnamomum aromaticum|Cassia]]
* [[Cinnamon]]
* [[Sassafras]]

;[[Berry|Berries]]
* [[Allspice]]
* [[Juniper]]

;[[Flower]]s
* [[Cannabis flower essential oil|Cannabis]]
* [[Chamomile]]
* [[Clary sage]]
* [[Clove]]
* [[Hops]]
* [[Hyssop]]
* [[Jasmine]]
* [[Lavender]]
* [[Leptospermum scoparium|Manuka]]
* [[Marjoram]]
* [[Orange (fruit)|Orange]]
* [[Pelargonium]] (Scented geranium)
* [[Plumeria]]
* [[Rose]]
* [[Ylang-ylang]]
| valign="top" |

;[[Leaf|Leaves]]
* [[Basil]]
* [[Bay leaf]]
* [[Buchu]]
* [[Cinnamon]]
* [[Common sage]]
* [[Eucalyptus]]
* [[Guava]]
* [[Lemon grass]]
* [[Melaleuca]]
* [[Oregano]]
* [[rose]]
* [[Bergamot orange|bergamot]]
* [[Patchouli]]
* [[Peppermint]]
* [[Pine]]
* [[Rosemary]]
* [[Spearmint]]
* [[Melaleuca alternifolia|Tea tree]]
* [[Thyme]]
* [[Tsuga]]
* [[Wintergreen]]
;[[Peel (fruit)|Peel]]
* [[Bergamot orange|Bergamot]]
* [[Grapefruit]]
* [[Lemon]]
* [[Lime (fruit)|Lime]]
* [[Orange (fruit)|Orange]]
* [[Tangerine]]
| valign="top" |

;[[Resin]]
<!-- not sure if fossilized tree resins count * [[Amber]] --><!-- not sure if a balsam would count or not * [[Myroxylon balsamum|Balsam Tolu]] -->

*[[Benzoin resin|Benzoin]]
* [[Copaiba]]
* [[Frankincense]]
* [[Labdanum]]
* [[Myrrh]]

;[[Rhizome]]

*[[Galangal]]
* [[Ginger]]

;[[Root]]s

*[[Valerian (herb)|Valerian]]

;[[Seed]]s

*[[Anise]]
* [[Buchu]]
* [[Celery]]
* [[Cumin]]
* [[Flax]]
* [[Nutmeg oil]]

;[[Wood]]s

*[[Agarwood]]
* [[Camphor]]
* [[Cedrus|Cedar]]
* [[Rosewood]]
* [[Sandalwood]]
|}

===Balsam of Peru===
[[Balsam of Peru]], an essential oil derived from ''[[Myroxylon]]'' plants, is used in food and drink for flavoring, in perfumes and toiletries for fragrance, and in animal care products.<ref>{{Cite web|date=11 December 2021|title=Balsam of Peru|url=https://go.drugbank.com/drugs/DB11482|publisher=DrugBank|access-date=2021-12-15|website=go.drugbank.com}}</ref> However, national and international surveys identified balsam of Peru among the "top five" allergens most commonly causing [[patch test]] allergic reactions in people referred to [[dermatology]] clinics.<ref name="Gottfried2008">{{cite book |title= Biocompatibility of Dental Materials |chapter= Diagnosis of Side Effects of Dental Materials, with Special Emphasis on Delayed and Immediate Allergic Reactions |chapter-url= https://books.google.com/books?id=mrreTHuo54wC&pg=PA352 |first1= D |last1= Arenholt-Bindslev |first2= R |last2= Jolanki |first3= L |last3= Kanerva |date= 2009 |editor-first1= Gottfried |editor-last1= Schmalz |editor-first2= Dorthe |editor-last2= Arenholt-Bindslev |publisher= Springer |page= 352 |access-date= March 5, 2014 |isbn= 978-3-540-77782-3 |doi= 10.1007/978-3-540-77782-3_14 |url-status= live |archive-url= https://web.archive.org/web/20160518233136/https://books.google.com/books?id=mrreTHuo54wC&pg=PA352 |archive-date= May 18, 2016 }}</ref><ref name="Habif2009">{{cite book|last=Habif|first=Thomas P.|url=https://books.google.com/books?id=kDWlWR5UbqQC&q=%22balsam+of+peru%22+allergy&pg=PT530|title=Clinical Dermatology|publisher=Elsevier Health Sciences|year=2009|isbn=978-0-323-08037-8|access-date=March 6, 2014}}</ref><ref>{{cite book|last1=Yiannias|first1=JA|title=Conn's Current Therapy 2014: Expert Consult|publisher=Elsevier Health Sciences|year=2013|isbn=978-0-323-22572-4|editor-last1=Bope|editor-first1=Edward T.|chapter=Contact Dermatitis|editor-last2=Kellerman|editor-first2=Rick D.|chapter-url=https://books.google.com/books?id=fmwYAgAAQBAJ&pg=PT264}}</ref>

===Garlic oil===
[[Garlic oil]] is an essential oil derived from [[garlic]].<ref name="Linskens Adams Crespo Jackson 2012 p. 105">{{cite book | last1=Linskens | first1=H.F. | last2=Adams | first2=R.P. | last3=Crespo | first3=M.E. | last4=Jackson | first4=J.F. | last5=Deans | first5=S.G. | last6=Dobson | first6=H.E.M. | last7=Dunlop | first7=P. | last8=Erdelmeier | first8=C.A.J. | last9=Ghosh | first9=A. | last10=Hammond | first10=E.G. | title=Essential Oils and Waxes | publisher=Springer Berlin Heidelberg | series=Molecular Methods of Plant Analysis | year=2012 | isbn=978-3-642-84023-4 | url=https://books.google.com/books?id=eKz1CAAAQBAJ&pg=PA105 | access-date=December 29, 2017 | page=105}}</ref>

===Eucalyptus oil===
{{main|Eucalyptus oil}}
Most eucalyptus oil on the market is produced from the leaves of ''Eucalyptus globulus''. Steam-distilled eucalyptus oil is used throughout Asia, Africa, Latin America and South America as a primary cleaning/disinfecting agent added to soaped mop and countertop cleaning solutions; it also possesses insect and limited vermin control properties.<ref>{{cite journal |title=Eucalyptus essential oil as a natural pesticide |first1=Daizy R. |last1=Batish |first2=Harminder Pal |last2=Singh |first3=Ravinder Kumar |last3=Kohlia |first4=Shalinder |last4=Kaur |journal=Forest Ecology and Management |volume=256 |issue=12 |date=10 December 2008 |pages=2166–2174 |doi=10.1016/j.foreco.2008.08.008 |bibcode=2008ForEM.256.2166B }}</ref> Note, however, there are hundreds of species of eucalyptus, and perhaps some dozens are used to various extents as sources of essential oils. Not only do the products of different species differ greatly in characteristics and effects, but also the products of the very same tree can vary grossly.<ref name=Thorpe1>{{cite book |title= Thorpe's Dictionary of Applied Chemistry |volume= 8 |edition= 4th |publisher= Longmans Green |year= 1947}}{{page needed|date= October 2014}}</ref>

===Lavender oil===
{{main|Lavender oil}}
[[File:Marchés des Producteurs de Pays 11 16 14.jpg|thumb|Lavender essential oil sold at a market in [[France]]]]
Lavender oil has long been used in the production of [[perfume]].<ref>N. Groom. New Perfume Handbook. Springer Science & Business Media, 1997 {{ISBN|9780751404036}}, pp. 184-186</ref> However, studies have shown it can be estrogenic and antiandrogenic, causing problems for prepubescent boys and pregnant women, in particular.<ref>{{cite journal|date=2007|title=Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils|journal=New England Journal of Medicine|volume=356|issue=5|pages=479–485|doi=10.1056/NEJMoa064725|pmid=17267908|last1=Henley|first1=Derek V|last2=Lipson|first2=Natasha|last3=Korach|first3=Kenneth S|last4=Bloch|first4=Clifford A|doi-access=free}}</ref> Lavender essential oil is also used as an insect repellent.<ref>{{cite book
 | title=Insect Repellents Handbook
 | editor1=Debboun, Mustapha
 | editor2=Frances, Stephen P.
 | editor3=Strickman, Daniel
 | publisher=CRC Press
 | year=2014
 | edition=2nd
 | isbn=978-1-4665-5355-2
 | page=362
}}</ref>

===Rose oil===
{{main|Rose oil}}
[[Rose oil]] is produced from the petals of  ''[[Rosa damascena]]'' and ''[[Rosa centifolia]]''. Steam-distilled rose oil is known as "rose otto", while the solvent extracted product is known as "rose absolute".

==Toxicity==
<!-- please consider updating the aromatherapy article's section on safety/danger when you update this. -->
The potential [[toxicity]] of essential oil is related to its level or grade of purity, and to the toxicity of specific chemical components of the oil.<ref name=poison.org/> Many essential oils are designed exclusively for their aroma-therapeutic quality; these essential oils generally should not be applied directly to the skin in their undiluted form.<ref name=poison.org/> Some can cause severe irritation, provoke an [[Allergy|allergic reaction]] and, over time, prove [[hepatotoxicity|toxic to the liver]]. If ingested or rubbed into the skin, essential oils can be highly poisonous, causing confusion, choking, loss of muscle coordination, difficulty in breathing, [[pneumonia]], [[seizure]]s, and possibly severe allergic reactions or [[coma]].<ref name=poison.org/>

Some essential oils, including many of the [[citrus peel]] oils, are [[photosensitizer]]s, increasing vulnerability of the skin to sunlight.<ref name="KadduKerl2001">{{cite journal |doi=10.1067/mjd.2001.116226 |pmid=11511848 |title=Accidental bullous phototoxic reactions to bergamot aromatherapy oil |journal=Journal of the American Academy of Dermatology |volume=45 |issue=3 |pages=458–61 |year=2001 |last1=Kaddu |first1=Steven |last2=Kerl |first2=Helmut |last3=Wolf |first3=Peter }}</ref>

Industrial users of essential oils should consult the [[safety data sheet]]s to determine the hazards and handling requirements of particular oils.<ref name=poison.org/> Even certain therapeutic-grade oils can pose potential threats to individuals with epilepsy or pregnant women.

Essential oil use in children can pose a danger when misused because of their thin skin and immature livers. This might cause them to be more susceptible to toxic effects than adults.<ref name="poison.org"/>

===Flammability===
The [[flash point]] of each essential oil is different.  Many of the common essential oils, such as tea tree, lavender, and citrus oils, are classed as [[HAZMAT Class 3 Flammable Liquids|Class 3 Flammable Liquid]]s, as they have a flash point of 50–60 °C.

===Gynecomastia===
[[Estrogen]]ic and [[antiandrogen]]ic activity have been reported by ''in vitro'' study of [[tea tree oil]] and [[lavender]] essential oils. Two published sets of case reports suggest that lavender oil may be implicated in some cases of [[gynecomastia]], an abnormal breast tissue growth in prepubescent boys.<ref>{{cite journal |doi=10.1056/NEJMoa064725 |pmid=17267908 |title=Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils |journal=New England Journal of Medicine |volume=356 |issue=5 |pages=479–85 |year=2007 |last1=Henley |first1=Derek V. |last2=Lipson |first2=Natasha |last3=Korach |first3=Kenneth S. |last4=Bloch |first4=Clifford A. |doi-access=free }}</ref><ref>{{cite journal |vauthors=Diaz A, Luque L, Badar Z, Kornic S, Danon M |s2cid=19454282 |title=Prepubertal gynecomastia and chronic lavender exposure: report of three cases |journal=J. Pediatr. Endocrinol. Metab. |volume=29 |issue=1 |pages=103–107 |date=2016 |pmid=26353172 |doi=10.1515/jpem-2015-0248 }}</ref> The European Commission's Scientific Committee on Consumer Safety dismissed the claims against tea tree oil as implausible, but did not comment on lavender oil.<ref>{{citation|author=Scientific Committee on Consumer Products|title=Opinion on tea tree oil|date=December 16, 2008|url=http://ec.europa.eu/health/archive/ph_risk/committees/04_sccp/docs/sccp_o_160.pdf|issue=Report No. SCCP/1155/08|publisher=[[Directorate-General for Health and Consumer Protection|Directorate-General for Health and Consumers]]: [[European Commission]]: [[European Union]]}}</ref> In 2018, a [[BBC]] report on a study stated that tea tree and lavender oils contain eight substances that when tested in tissue culture experiments, increasing the level of [[estrogen]] and decreasing the level of [[testosterone]]. Some of the substances are found in "at least 65 other essential oils". The study did not include animal or human testing.<ref>{{Cite news|title=More evidence essential oils 'make male breasts develop'|url=https://www.bbc.co.uk/news/health-43429933|publisher=BBC|access-date=18 March 2018|date=18 March 2018|quote=A suspected link between abnormal breast growth in young boys and the use of lavender and tea tree oils has been given new weight, after a study found eight chemicals contained in the oils interfere with hormones.|work=BBC News}}</ref>

===Handling===
Exposure to essential oils may cause [[contact dermatitis]].<ref name="ReferenceA"/><ref name="ReferenceB"/><ref name="ReferenceC"/> Essential oils can be aggressive toward rubbers and plastics, so care must be taken in choosing the correct handling equipment. Glass syringes are often used, but have coarse volumetric graduations. [[Pipette#Pipetting syringe|Chemistry syringes]] are ideal, as they resist essential oils, are long enough to enter deep vessels, and have fine graduations, facilitating quality control. Unlike traditional pipettes, which have difficulty handling viscous fluids, the chemistry syringe, also known as a positive displacement pipette, has a seal and piston arrangement which slides inside the pipette, wiping the essential oil off the pipette wall.

===Ingestion===
Some essential oils qualify as [[GRAS]] flavoring agents for use in foods, beverages, and confectioneries according to strict [[good manufacturing practice]] and [[flavorist]] standards.<ref name="US FDA">{{Cite web|url=https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=182.20|archive-url=https://web.archive.org/web/20030915162222/http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=182.20|url-status=dead|archive-date=September 15, 2003|title=CFR - Code of Federal Regulations Title 21|website=www.accessdata.fda.gov|access-date=2018-12-08}} {{PD-notice}}</ref> [[Pharmacopoeia]] standards for medicinal oils should be heeded. Some oils can be toxic to some domestic animals, cats in particular.<ref>{{cite journal |doi=10.1177/104063879801000223 |pmid=9576358 |title=Australian Tea Tree (Melaleuca Alternifolia) Oil Poisoning in Three Purebred Cats |journal=Journal of Veterinary Diagnostic Investigation |volume=10 |issue=2 |pages=208–10 |year=1998 |last1=Bischoff |first1=K. |last2=Guale |first2=Fessesswork |doi-access=free }}</ref> The internal use of essential oils can pose hazards to pregnant women, as some can be [[abortifacient]]s in dose 0.5–10 mL, and thus should not be used during pregnancy.{{Citation needed|date=December 2018}}

===Pesticide residues===
Concern about [[pesticide]] residues in essential oils, particularly those used therapeutically, means many practitioners of aromatherapy buy [[Organic farming|organically]] produced oils. Not only are pesticides present in trace quantities, but also the oils themselves are used in tiny quantities and usually in high dilutions. Where there is a concern about pesticide residues in food essential oils, such as mint or orange oils, the proper criterion is not solely whether the material is organically produced, but whether it meets the government standards based on actual analysis of its pesticide content.<ref>{{cite book |last= Menary |first= RC |title= Minimising pesticide residues in essential oils |year= 2008 |publisher= Rural Industries Research and Development Corporation |isbn= 978-1-74151-709-5}}{{page needed|date= October 2014}}</ref>

===Pregnancy===
Some essential oils may contain impurities and additives that may be harmful to pregnant women.<ref>{{Cite journal|date=2013|title=Management of severe nausea and vomiting in pregnant women|journal=Clinical Pharmacist|doi=10.1211/cp.2013.11131205|issn=2053-6178}}</ref> Certain essential oils are safe to use during [[pregnancy]], but care must be taken when selecting quality and brand.  Sensitivity to certain smells may cause pregnant women to have adverse side effects with essential oil use, such as headache, [[vertigo]], and nausea. Pregnant women often report an abnormal sensitivity to smells and taste,<ref>{{cite journal|last1=Nordin|first1=S.|last2=Broman|first2=D. A.|last3=Olofsson|first3=J. K.|last4=Wulff|first4=M|year=2004|title=A Longitudinal Descriptive Study of Self-reported Abnormal Smell and Taste Perception in Pregnant Women|journal=Chemical Senses|volume=29|issue=5|pages=391–402|doi=10.1093/chemse/bjh040|pmid=15201206|doi-access=free}}</ref> and essential oils can cause irritation and nausea when ingested.<ref name=poison.org/>

===Toxicology===
The following table lists the {{LD50}} or median lethal dose for common oils; this is the dose required to kill half the members of a tested animal population. LD<sub>50</sub> is intended as a guideline only, and reported values can vary widely due to differences in tested species and testing conditions.<ref>{{Cite journal |url= http://www.zenitech.com/documents/Toxicity_of_essential_oils_p1.pdf |title= Toxicology of essential oils reviewed |date= September 2009 |journal= Personal Care |first= AC |last= Dweck |url-status= dead |archive-url= https://web.archive.org/web/20110718152502/http://www.zenitech.com/documents/Toxicity_of_essential_oils_p1.pdf |archive-date= 2011-07-18 |access-date= 2011-01-05 }}</ref>
{| class="wikitable"
|-
! Common Name !! Oral LD<sub>50</sub>!! Dermal LD<sub>50</sub> !! Notes
|-
| [[Neem]] || 14 g/kg|| >2 g/kg ||
|-
| [[Lemon myrtle]] || 2.43 g/kg || 2.25 g/kg ||
|-
| [[Frankincense]] || >5 g/kg || >5 g/kg || ''Boswellia carterii''
|-
| Frankincense || >2 g/kg || >2 g/kg || ''[[Boswellia sacra]]''
|-
| Indian frankincense || >2 g/kg || >2 g/kg || ''[[Boswellia serrata]]''
|-
| [[Ylang-ylang]] || >5 g/kg || >5 g/kg ||
|-
| [[Cedarwood]] ||  >5 g/kg ||  >5 g/kg ||
|-
| [[Roman chamomile]] || >5 g/kg || >5 g/kg ||
|-
| White camphor || >5 g/kg || >5 g/kg || ''[[Camphora officinarum|Cinnamomum camphora]]'', extracted from leaves
|-
| Yellow camphor || 3.73 g/kg || >5 g/kg || ''Cinnamomum camphora'', extracted from bark
|-
| Hot oil || 3.80 g/kg || >5 g/kg || ''Cinnamomum camphora'', oil extracted from leaves
|-
| Cassia || 2.80 g/kg || 0.32 g/kg ||
|}

==Standardization of derived products==
In 2002, [[International Organization for Standardization|ISO]] published ISO 4720 in which the [[botanical name]]s of the relevant plants are standardized.<ref name="eoni">{{cite web|title=ISO 4720:2002 Essential oils – Nomenclature|url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?ics1=01&ics2=040&ics3=71&csnumber=30435|author=International Organization for Standardization|author-link=International Organization for Standardization|access-date=April 23, 2009}}</ref> The rest of the standards with regards to this topic can be found in the section of ICS 71.100.60 <ref name="eo">{{cite web|title=71.100.60: Essential oils|url=http://www.iso.org/iso/products/standards/catalogue_ics_browse.htm?ICS1=71&ICS2=100&ICS3=60&|author=International Organization for Standardization|author-link=International Organization for Standardization|access-date=June 14, 2009}}</ref>

{{Further|British Pharmacopoeia|United States Pharmacopoeia}}

==History==
{{more citations|section|date=November 2021}}

The resins of aromatics and plant extracts were retained to produce [[traditional medicine]]s and scented preparations, such as perfumes and incense, including [[frankincense]], [[myrrh]], cedarwood, juniper berry and cinnamon in ancient Egypt may have contained essential oils.<ref name="BaserBuchbauer2009">{{cite book | author1 = K. Husnu Can Baser | author2 = Gerhard Buchbauer | date = 28 December 2009 | title = Handbook of Essential Oils: Science, Technology, and Applications | publisher = CRC Press | pages = | isbn = 978-1-4200-6316-5 | url = https://books.google.com/books?id=2AEtSKfB2nUC}}</ref><ref name="Rubin2017">{{cite book | author = Jordan Rubin | date = 17 January 2017 | title = Essential Oils: Ancient Medicine for a Modern World | publisher = Destiny Image Publishers | pages = | isbn = 978-0-7684-1188-1 | url = https://books.google.com/books?id=tteTDgAAQBAJ&pg=PT48}}</ref> In 1923, when archaeologists opened Pharaoh [[Tutankhamun]]’s tomb, they found 50 alabaster jars of essential oils.<ref name="Rubin2017"/>{{dubious|date=November 2021}}

Essential oils have been used in [[folk medicine]] over centuries. The Persian physician [[Avicenna|Ibn Sina]], known as Avicenna in Europe, was first to derive the fragrance of flowers from distillation,<ref>{{Cite book|url=https://books.google.com/books?id=WMvVBi5EbhMC&q=attar+perfume+muslim&pg=PA70|title=Studies in Islamic Civilization: The Muslim Contribution to the Renaissance|last1=Essa|first1=Ahmed|last2=Ali|first2=Othman|date=2010|publisher=International Institute of Islamic Thought (IIIT)|isbn=978-1-56564-350-5|language=en|page=70}}</ref> while the earliest recorded mention of the techniques and methods used to produce essential oils may be [[Ibn al-Baitar]] (1188–1248), an [[Arab]] [[Al-Andalus]]ian (Muslim Spain) [[physician]], [[pharmacist]] and [[chemist]].<ref name="Houtsma1993">{{cite book |first= M.Th. |last= Houtsma |title= E. J. Brill's First Encyclopaedia of Islam, 1913–1936 |volume= 4 |year= 1993 |publisher= [[Brill Publishers|Brill]] |isbn= 978-90-04-09790-2 |pages=1011– }}</ref>

Rather than refer to essential oils themselves, modern works typically discuss specific chemical compounds of which the essential oils are composed, such as referring to [[methyl salicylate]] rather than "oil of wintergreen".<ref name="G&G">{{cite book |editor1-last=Gilman |editor1-first=A. G. |editor2-last=Rall |editor2-first=T. W. |editor3-last=Nies |editor3-first=Alan S. |editor4-last=Taylor |editor4-first=Palmer |title=Goodman & Gilman's The Pharmacological Basis of Therapeutics |edition=8th |publisher=[[Pergamon Press|Pergamon]] |location=New York |year=1990 |isbn=978-0-08-040296-3|title-link=Goodman & Gilman's The Pharmacological Basis of Therapeutics }} {{page needed|date= October 2014}}</ref><ref name="isbn0-07-105239-9">{{cite book |last1= Klaassen |first1= Curtis D. |last2= Amdur |first2= Mary O. |last3= Casarett |first3= Louis J. |last4= Doull |first4= John |title= Casarett and Doull's Toxicology: The Basic Science of Poisons |publisher= McGraw-Hill |location= New York |year= 1991 |isbn= 978-0-07-105239-9}}{{page needed|date= October 2014}}</ref>

Essential oils are used in [[aromatherapy]], a branch of [[alternative medicine]] that uses essential oils and other aromatic compounds.<ref>{{Cite web|date=2017-03-20|title=Aromatherapy: Uses, benefits, oils, and risks|url=https://www.medicalnewstoday.com/articles/10884|access-date=2022-02-16|website=www.medicalnewstoday.com|language=en}}</ref> Oils are volatilized, diluted in a [[carrier oil]] and used in massage, diffused in the air by a [[nebulizer]] or diffuser,  heated over a candle flame, or burned as incense.

==See also==
{{Commons category|Essential oils}}
{{Wikibooks|Complete Guide to Essential Oils}}
* [[Aroma lamp]]
* [[Enfleurage]]
* [[Fragrance oil]]
* [[List of essential oils]]
* [[Tincture]]
* [[Volatility (chemistry)|Volatility]]

==References==
{{Reflist}}

==Further reading==
* {{cite book
 | author=Baser, K.H.C. 
 | author2=G. Buchbauer
 | title=Handbook of Essential Oils: Science, Technology and Applications
 | publisher=CRC Press, Boca Raton, London, New York
 | year=2010
 | isbn= 978-1-4200-6315-8
}}
* {{cite book
 | author=Schnaubelt, Kurt
 | title=Advanced Aromatherapy: The Science of Essential Oil Therapy
 | publisher=Healing Arts Press
 | year=1999
 | isbn= 978-0-89281-743-6
}}
* {{cite book
 | author=Sellar, Wanda
 | title=The Directory of Essential Oils
 | location=Essex
 | publisher=The C.W. Daniel Company, Ltd.
 | edition=Reprint
 | year=2001
 | isbn= 978-0-85207-346-9
}}
* {{cite book
 | author=Tisserand, Robert
 | title=Essential Oil Safety: A Guide for Health Care Professionals
 | publisher=Churchill Livingstone
 | year=1995
 | isbn= 978-0-443-05260-6
}}
* {{cite journal|last1=Rimal|first1=Vishal|last2=Shishodia|first2=Shubham|last3=Srivastava|first3=Prem Kumar|last4=Gupta|first4=Subhadeep|last5=Mallick|first5=Amirul Islam|title=Synthesis and characterization of Indian essential oil Carbon Dots for interdisciplinary applications|journal=Applied Nanoscience|volume=11|issue=4|year=2021|pages=1225–1239|issn=2190-5509|doi=10.1007/s13204-021-01737-3|bibcode=2021ApNan..11.1225R|s2cid=232145772}}

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{{DEFAULTSORT:Essential Oil}}
[[Category:Essential oils| ]]