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Tuesday, May 13, 2008

Essential oil chemistry

Essential oils are very complex in nature having many chemical ingredients. Some play a major part and others a minor part. The ingredients found in essential oils are organic due to their molecular structure which is based on carbon atoms held together by hydrogen atoms. Oxygen atoms and sometimes nitrogen and sulphur atoms are also present.

It is useful to be familiar with the basic chemical structure of essential oils so you will know it's therapeutic qualitiesas well as any possible hazardous effects.

Below is a list of the main chemical components found in essential oils and information on each one:


These chemicals are found in most essential oils, with citrus oils having a very large percentage of them. They have high antiseptic and tonic qualities and are very good air purifiers.

Monoterpenes contain 10 carbon atoms. They are colorless and highly volatile. They can deteriorate very quickly therefore need to be kept at cool temperatures. Examples of monoterpenes are limonene (found in most citrus oils such as lemon), pinene (found in pine), and camphene (found in camphor).


These terpenes are not as volatile as monoterpenes. They contain 15 carbon atoms (hence the name 'sesqui' which means one and a half). Sesquiterpenes have a calming effect as well as being antiinflammatory and anti-infectious.

Examples of these include zingiberene (found in ginger), cedrene (found in cedarwood), and caryophellene (found in clove).


Phenols are the most antiseptic chemicals found in plants. They stimulate the body and can be beneficial in small doses however large doses can be a poison to the nervous system. Large doses can also cause skin irritations as well as digestive discomfort to sensitive people.

Examples of phenols are thymol (found in thyme), and eugenol (found in clove).


Alcohols are also highly antiseptic, antibacterial, anti-fungal and antibiotic. They are a good tonic to the nervous system and can stimulate the immune response.

They are far less aggressive than phenols and examples include lavendulol (found in lavender), nerol (found in neroli), and geraniol (found in geranium).

Ethers / Esters

Ethers are much stronger than esters but both have similar properties. They are a powerful antispasmodic, antibacterial, and anti-inflammatory. They are very gentle on the skin and particularly efficient in relaxing and rebalancing the nervous system.

Examples of ethers and esters include cinnamyl acetate (found in cinnamon), and myrtinyl acetate (found in myrtle).


In small doses, ketones can relax and sedate. They can promote the healing of scar tissues and are known to be anticoagulants. They can be useful in stimulating the immune system as well as treating respiratory complaints.

In large doses, however, they can have the opposite effect and can be a poison to the nervous system. This can cause miscarriage, convulsions, and even epileptic fits.

Examples of ketones include thyone (found in sage), pinocamphone (found in hyssop), and carvone (found in peppermint).


The properties of aldehydes are similar to the properties of both alcohols and ketones. They can calm the nervous system and they are anti-inflammatory.

Aldehydes can be quite harsh however, and can cause major irritation to both the skin and mucous membranes.

Examples include furfurol (found in lavender, sandalwood, cinnamon and cypress), and aldehyde benzoic (found in benzoin)


These chemicals have a relaxing and sedative effect. They are known to have properties that are anticonvulsant and anti-coagulant.

Coumarins, in particular, furocourmains can be photosensitive therefore it is best to avoid exposure to the sun when using essential oils with these constituents.

Examples of coumarins include bergaptene (found in bergamot), angelicine (found in angelica), and citroptene (found in most citrus oils).

Hazardous essential oils

Below is a list of oils that are not to be used in the practice of aromatherapy:

  • Almond (bitter) Prunus amygdalus
  • Boldo leaf Peunus boldus
  • Calamus Acorus calmus
  • Camphor Cinnamomum camphora
  • Horseradish Cochlearia armorica
  • Jaborandi leaf Pilocarpus jaborandi
  • Mugwort Artimesia vulgaris
  • Mustard Brassica nigra
  • Pennyroyale Mentha pulegium
  • Rue Ruta graveolens
  • Sassafras Sassafras albidum
  • Savin Ocotea cymbarum
  • Tansy Artemisia abrotanum
  • Thuya Thuya occidentalis / plicata
  • Wormwood Artemisia absinthium

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