The Chemistry of Essential Oils

Chemistry of Essential Oils

The Science of Chemical Components in an Aromatherapy Oil

Essential oils are a complex make-up of many chemical components; pure essential oils, extracted from plants and which remain unadulterated, hold many chemical combinations. Science has attempted to copy, isolate or substitute individual chemical components of essential oils but is unable to replicate the therapeutic value of a pure essential oil; many essential oils are so complex in their chemistry that science has, so far, been unable to identify every single chemical component in some essential oils.

The Therapeutic Value of Essential Oils

Essential oils work in many ways but the key to the therapeutic value of an essential oil is held in the chemistry of an essential oil; rose essential oil has some of the most complex chemical components and, although many fragrance oils attempt to mimic the fragrance of rose, none can duplicate the healing properties.

Essential Oil Components

All essential oils are made up of carbon, oxygen and hydrogen atoms; the chemistry of essential oils is complex but, in simple terms, all essential oils hold a combination of molecules made up of the following chemical components:

  • alcohols
  • ketones
  • phenols
  • acids
  • esters
  • aldehydes
  • coumarins
  • furanocoumarins.

Alcohols in Essential Oils

An alcohol is formed in an essential oil from a complex combination of hydrogen and oxygen molecules; alcohols in an essential oil can be further categorized into monoterpenols, sesquiterpenols and diterpenols and the alcohol name usually ends in -ol.

In therapeutic terms, alcohols are considered to be stimulating, anti-viral, bactericidal, anti-infectious and a tonic. In general, essential oils which are mainly composed of alcohol are non-toxic, non-irritant and are safe to use with children and older people; however, it is always advisable to consult a qualified professional on individual use of essential oils.

Ketones in Essential Oils

Ketone names usually end in -one, although there are exceptions to this general rule. Unlike alcohols, ketones are to be treated with caution; scientifically, there is no conclusive proof that all ketones are hazardous and ketones do not frequently occur in essential oils in high quantities but the following essential oils, which contain ketones, should be used with care:

  • tansy
  • rue
  • sage
  • hyssop
  • caraway
  • aniseed

Ketones, when used with care, are considered to be calming, sedative, digestive, analgesic, stimulant, expectorant, wound healing and anti-inflammatory in therapeutic value; ketones vary and some may possess more of these properties than others, so it is advisable to know the individual essential oil being used and the actual ketones it possesses.

Phenols in Essential Oils

Phenols are similar to alcohols in essential oils but are stronger in their actions; confusingly, phenol names also end in -ol so it is essential to identify the individual chemical component and know if it is an alcohol or a phenol. Phenol properties include being antiseptic, bactericidal and a stimulant; however, phenols can be an irritant if overused in large quantities.

Acids and Esters in Essential Oils

Acids rarely materialize individually in any significant amount in essential oils but are anti-inflammatory in their actions; the combination of acids and esters is more common in essential oils. Esters, usually ending in the suffix -ate, are generally anti-inflammatory, calming, balancing, useful in skin care, anti-fungal, non-toxic and gentle to use.

Aldehydes in Essential Oils

Aldehyde names end in -al; aldehydes are probably known for their use in perfumery as they are powerful both in fragrance and in properties. Consequently, when used for their therapeutic values in aromatherapy, aldehydes should be used with the same caution as ketones, although they are not as toxic as ketones. Aldehydes are considered to be anti-infectious, tonic, anti-inflammatory and calming; aldehydes may be an irritant and cause sensitization in some individuals.

Coumarins and Furocoumarins in Essential Oils

Coumarins possess the properties of being calming, sedative and anti-coagulant; furocoumarins are are phototoxic and essential oils which possess furocoumarins should not be used in exposure to sunlight. Bergamot essential oil contains the best example of the chemical component of furocoumarins (that of bergapten).

The Science of Essential Oils

Some essential oils may contain minute quantities of other chemical components such as ethers, oxides and lactones, in addition to the main chemical components mentioned above. In aromatherapy, chemical components of essential oils are not used individually but with a combination of one or more other chemical components. Science is still studying the therapeutic properties of the individual chemical components and providing conclusive results; however, certain essential oils demonstrate these therapeutic properties when used.

The Power of Essential Oils

Combining both the individual chemical components found in essential oils and a number of different essential oils produces varying therapeutic effects (also known as a synergistic effect); knowing the chemistry of the individual chemical components of essential oils and the general properties which they possess helps in using essential oils both effectively and safely.


Price, Shirley 2000 Aromatherapy Workbook UK:Thorsons

Price, Shirley, Price, Len 2001 Aromatherapy for Health Professionals UK: Churchill Livingstone

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