Raw Materials

Main article: List of essential oils

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

Berries

* Allspice
* Juniper

Seeds

* Almond
* Anise
* Celery
* Cumin
* Nutmeg oil

Bark

* Cassia
* Cinnamon
* Sassafras

Wood

* Camphor
* Cedar
* Rosewood
* Sandalwood
* Agarwood

Rhizome

* Galangal
* Ginger



Leaves

* Basil
* Bay leaf
* Cinnamon
* Common sage
* Eucalyptus
* Lemon grass
* Melaleuca
* Oregano
* Patchouli
* Peppermint
* Pine
* Rosemary
* Spearmint
* Tea tree
* Thyme
* Wintergreen

Resin

* Frankincense
* Myrrh



Flowers

* Cannabis
* Chamomile
* Clary sage
* Clove
* Scented geranium
* Hops
* Hyssop
* Jasmine
* Lavender
* Manuka
* Marjoram
* Orange
* Rose
* Ylang-ylang

Peel

* Bergamot
* Grapefruit
* Lemon
* Lime
* Orange
* Tangerine

Root

* Valerian

Eucalyptus oil
Main article: Eucalyptus oil

The most well-known essential oil world-wide is eucalyptus oil, produced from the leaves of "Eucalyptus globulus". Steam-distilled eucalyptus oil is utilized throughout Asia, Africa, Latin America and South America as a primary cleaning/disinfecting agent added to soaped mop and countertop cleaning solutions, possessing insect and limited vermin control properties.
Rose oil
Main article: Rose oil

The 2nd most well-known essential oil is probably rose oil, 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".

Dangers

Because of their concentrated nature, essential oils generally should not be applied directly to the skin in their undiluted or "neat" form. Some can cause severe irritation, provoke an allergic reaction and over time prove hepatotoxic. Essential oils should not be used with animals as they possess extreme hepatotoxicity and dermal toxicity for animals, especially for cats. Instead, essential oils should be blended with a vegetable-based "carrier" oil (a.k.a., a base, or "fixed" oil) before being applied. Common carrier oils include olive, almond, hazelnut and grapeseed. Only neutral oils should be used. A common ratio of essential oil disbursed in a carrier oil is 0.5–3% (most under 10%), depending on its purpose. Some essential oils, including many of the citrus peel oils, are photosensitizers, increasing the skin's vulnerability to sunlight. Industrial users of essential oils should consult the material safety data sheets (MSDS) to determine the hazards and handling requirements of particular oils.

Handling

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. 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 has a seal and piston arrangement which slides inside the pipette, wiping the essential oil off the pipette wall. This improves accuracy, and the inside of the pipette is easy to clean and reuse immediately. Chemistry pipetting syringes are equal in accuracy to the best laboratory equipment and are available in sizes from 1 mL through 25 mL.

Pregnancy

The use of essential oils in pregnancy is not recommended due to inadequate published evidence to demonstrate evidence of safety.
Gynecomastia

Estrogenic and antiandrogenic activity have been reported by in vitro study of tea tree oil and lavender essential oils. Case reports suggest that the oils may be implicated in some cases of gynecomastia, an abnormal breast tissue growth, in prepubescent boys.
Pesticide residues

There is some concern about pesticide residues in essential oils, particularly those used therapeutically. For this reason, many practitioners of aromatherapy buy organically produced oils.[citation needed]

Ingestion

Essential oils are used extensively as GRAS flavoring agents in foods, beverages and confectionaries according to strict GMP (Good Manufacturing Practice) and flavorist standards, and while some advocate the ingestion of essential oils for therapeutic purposes in extremely small amounts, this should never be done except under the supervision of someone licensed to prescribe such treatment and/or who is well versed and experienced in "clinical" aromatherapy. Some common essential oils such as Eucalyptus are toxic internally. Pharmacopoeia standards for medicinal oils should be heeded. Some oils can be toxic to some domestic animals, cats in particular. The internal use of essential oils can pose hazards to pregnant women, as some can be abortifacients in dose 0.5–10 ml, and thus should not be used during pregnancy.

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 a Class 3 Flammable Liquid as they have a flash point of 50–60 °C.
Toxicology

LD50 of most essential oils or their main components are 0.5–10 mg/kg (orally or skin test).[citation needed] This compares with, for example, the LD50 of arsenic acid, one of the most common arsenic based poisons which is 6 mg/kg (as tested on rabbits).
Standardization of its derived products

In 2002, ISO published ISO 4720 in which the botanical names of the relevant plants are standardized . The rest of the standards with regards to this topic can be found in the section of ICS 71.100.60