Essential oil: Encyclopedia - Essential oil

Essential oil

An essential oil is a concentrated, hydrophobic liquid containing volatile aromatic compounds extracted from plants. It may be produced by distillation, expression, or solvent extraction. Essential oils are used in perfumery, aromatherapy, cosmetics, incense, medicine, household cleaning products, and for flavoring food and drink. They are valuable commodities in the fragrance and food industries.

Essential oil is also known as volatile oil and ethereal oil. It may also be referred to as "oil of" the raw plant material from which it was extracted, such as oil of clove.

Essential oil - Production

Main high-volume products - turpentine; orange, lemon, mint and citronella are essential oils. Prior to the discovery of distillation, essential oils were extracted by pressing, and this is still the case in cultures such as Egypt. Traditional Egyptian practice involves pressing the plant material, and then burying it in unglazed ceramic vessels in the desert for a period of months to drive out water, the water having a smaller molecular size diffuses through the ceramic vessels while the larger essential oils do not. The lotus oil in Tutankhamun's tomb, which retained its scent after 3000 years sealed in alabaster vessels, was pressed in this manner.

Today, most common essential oils, such as lavender, peppermint, and eucalyptus, are distilled. Raw plant material, consisting of the (flowers, leaves, wood, bark, roots, seeds, or peel, is put into an alembic (distillation apparatus) over water, and the volatile compounds are vaporized as the water is heated. The vapor flows into a cooling tank, and as the steam condenses, the essential oil, which is lighter than water, floats on top. The water is referred to as a hydrosol, hydrolat, or plant water essence. Popular hydrosols are rose water, lavender water, and orange blossom water. Most oils are distilled in a single process. One exception is ylang-ylang, which takes 22 hours to complete distillation. It is fractionally distilled, producing several grades.

Most citrus peel oils are usually expressed mechanically, or cold-pressed. These oils are usually by-products of the large-scale citrus industry, and thus are much cheaper than most distilled oils.

Some flowers contain very little volatile oil, or EO components are too delicate to be distilled. Instead, a solvent such as hexane or supercritical carbon dioxide is used to extract a concrete, or mixture of essential oil and other lipophilic (oil soluble) plant material. The solvent is then removed by distillation for re-use. Then another solvent, often ethyl alcohol, is used to extract the essential oil from the concrete. The alcohol is removed by a second distillation, leaving behind the absolute. Hence these types of essential oils, from plants such as jasmine and rose, are called absolutes.

In supercritical fluid extraction, high pressure carbon dioxide gas (up to 100 atm.) is used as a solvent. This avoids petrochemical residues in the extracted product and is identical to one of the techniques for making decaffeinated coffee.

Essential oil - Perfumery

Many essential oils are used in perfumery. The most well-known essential oil in perfumery is Rose, or Rose absolute. It takes many pounds of rose petals to distill one ounce of essential oil. To mitigate the cost, Rose oil is often diluted with Geranium essential oil, at varying ratios of up to one drop of Rose to ten drops of Geranium. This is referred to as extending the Rose fragrance. Since Rose and Geranium are complementary, the extending process does not dilute the Rose fragrance dramatically. Sometimes rose oil is adulterated with synthetic chemicals, such as phenylethanol, which is also a natural component of rose oil. This may be done to compensate for chemotype, e.g. Bulgarian distilled Rose oil is naturally low in phenylethanol, and Ukrainian Rose absolute is naturally high in phenylethanol. Most Rose oil is produced in Bulgaria and Morocco. Recently, China has begun cultivating Rose oil as well.

Essential oil - Aromatherapy

Aromatherapy is a form of herbal medicine, in which healing effects are ascribed to the aromatic compounds in essential oils and other plant extracts. Many common essential oils have medicinal properties that have been applied in folk medicine since ancient times and are still widely used today. For example, many essential oils have antiseptic properties, though some are stronger than others. In addition, many have an uplifting effect on the mind, though different essential oils have different properties.

The purest oils with hardly standarized content of components are pharmacopeia grade essential oils. Undiluted essential oils suitable for aromatherapy are termed therapeutic grade. Since essential oils are so potent, many can irritate the skin unless diluted with a carrier oil. Fat plant oils (sweet almond oil, olive oil, hazelnut, rosehip seed, etc.) are examples of carrier oils. A home test to determine whether an oil is therapeutic grade is to place a drop on a coffee filter. Since the components of distilled essential oil are volatile substances, the oil will dissipate without leaving an oily residue on the paper. However, cold-pressed essential oils and absolutes may leave a spot.

Therapeutic grade is not a sole determination of quality. For example, Indian Sandalwood is considered more desirable than Australian Sandalwood, based upon the aroma; and is twice as costly, mainly because Indian Sandalwood is endangered. Organic and wild harvested essential oils also tend to be more expensive.

Essential oil - Popular uses

• Basil is used in perfumery for its clear, sweet and mildly spicy aroma. In aromatherapy, it is used for sharpening concentration, for its uplifting effect on depression, and to relieve headaches and migraines. Basil oil has many chemotypes and some are known to be emmenagogues and should be avoided during pregnancy.
• Bergamot is one of the most popular oils in perfumery. It is an excellent insect repellent and may be helpful for both the urinary tract and for the digestive tract. It is useful for skin conditions linked to stress, such as cold sores and chicken pox, especially when combined with eucalyptus oil. Bergamot is a flavoring agent in Earl Grey tea. But cold-pressed Bergamot oil contains bergaptene, a strong photosensitizer when applied to the skin, so only distilled or 'bergaptene-free' types can be topically used.
• Black pepper has a sharp and spicy aroma. Common uses include stimulating the circulation and for muscular aches and pains. Skin application is useful for bruises, since it stimulates the circulation.
• Citronella oil, obtained from a relative of lemongrass, is used as an insect repellant and in perfumery.
• Tea tree, eucalyptus, sandalwood oil, and many other essential oils have topical (external) antimicrobial (i.e. antibacterial, antifungal, antiviral, or antiparasitic) activity and are used as antiseptics and disinfectants.
• Clove oil is a topical analgesic, especially useful in dentistry. It is also used an antiseptic, antispasmodic, carminative, and antiemetic.
• Lavender oil is used as an antiseptic and for a number of other folk medicinal uses.
• Yarrow oil is used to reduce joint inflammation and relieve cold and influenza symptoms.

Essential oil - Dangers

The smoke from burning essential oils may contain potential carcinogens, such as polycyclic aromatic hydrocarbons (PAHs). Essential oils are naturally high in volatile organic compounds (VOCs). The internal use of essential oils should be fully avoided during pregnancy without consulting with a licensed professional, as some can be abortifacients in dose 0.5–10 ml.

Toxical data: LD50 of most EO or their main components are 0.5-10 g/kg (orally or skin test).

Essential oils should generally not be applied directly to the skin due to their rapid absorption rate. Instead, essential oil should be applied with a plants oils or other fats (carrier oil), such as olive, hazelnut, or any other "soft" oil. Common ratio of essential oil disbursed in a carrier oil is 0.5–3% (most less than 10%) and depends on its purpose. Some pressed essential oils, like bergamot, are photosensitizers, increasing the skin's reaction to sunlight and making it more likely to burn.

Industrial users of essential oils should consult the material safety data sheets (MSDS) to determine the hazards and handling requirements of particular oils.

There is some concern about pesticide residues in essential oil, particularly for therapeutic use. For this reason, many practitioners of aromatherapy choose to buy organically produced oils.

While some advocate the ingestion of essential oils for therapeutic purposes, this is generally not advisable in aromatherapy use. In medicine some oils use internally in dilution (dill, anise, star anise, mint oils etc.) In Pharmakopoeia we see standards for medicinal oils. Children are very sensitive to essential oils so dosages should be low. Also it can be toxic for some domestic animals, cats in particular. Owners must ensure that their pets do not come into contact with potentially harmful essential oils. [1]

Essential oil - Raw Materials

• Allspice berry
• Almond seed
• Anise seed
• Basil leaf
• Bay leaf
• Bergamot peel
• Camphor wood
• Cedar wood
• Celery seed
• Chamomile flower
• Cassia bark
• Citronella
• Cinnamon leaf or bark
• Clary sage flowering tops
• Clove bud
• Cumin seed
• Eucalyptus leaf
• Frankincense resin
• Geranium flower
• Ginger rhizome
• Grapefruit peel
• Hyssop flower
• Jasmine flower
• Juniper berry
• Lavender flower
• Lemon peel
• Lemon grass leaf
• Manuka flower
• Marjoram flower
• Melaleuca leaves
• Myrrh resin
• Nutmeg oil seed
• Orange, peel, flower (neroli), leaf (petitgrain)
• Oregano leaf
• Patchouli leaf
• Peppermint leaf
• Pine leaf
• Rose flower
• Rosemary leaf
• Rosewood wood
• Common sage leaf
• Sandalwood wood
• Spearmint leaf
• Tangerine peel
• Tea tree leaf
• Thyme leaf
• Wintergreen leaf
• Ylang-ylang flower

See also

• Complementary and alternative medicine
• Enfleurage
• Fragrance oil

Adapted from the Wikipedia article "Essential oil", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki