Essential oil components:

Without some knowledge of the components of essential oils, aromatherapy is not possible: ignoring some negative aspects of some components could even be dangerous!

Distiller Henri Viaud was one of the first to clearly mention it in his small book in 1983, later the book of Franchomme and Dr Penoel prepared the way to a real science of aromatherapy.

It is not the intention to give a lesson in organic chemistry here, but a brief explanation of the building blocks of essential oils will be helpfull. Carbon, hydrogen, oxygen are essential to life itself, and all three are contained in every essential oil. They combine in countless mono- and sesquiterpenic families of hydrocarbons, alcohols, ketones, acids, phenols, esters and coumarins (and furocoumarins).

A brief survey of the components of essential oils:


Aliphatic chains

Terpenic hydrocarbons are generally recognizable from their name: all end in -ene. They are all slightly antiseptic and bactericidal, analgesic, expectorant and stimulating.


Antiseptic, bactericidal, antiinflammatory, calming and slight hypotensors, some are analgesic and/or spasmomytic.


Expectorant, purgative, some are antifungal and antiviral. Some appear to have a balancing effect on the hormonal system, e.g. the diterpenic alcohol sclareol in Salvia sclareo(Clary) and also the sesquiterpenic alcohol viridiflorol in Melaleuca viridiflora(Niaouli).


Antiinfective, strongly bactericidal, antiviral and stimulating; they are generally nontoxic in use and do not cause skin irritation.


They are antiseptic and bactericidal. Because they stimulate both the nervous system (making them effective against depressive illness) and the immune system, they activate the body's own healing process.

They can be toxic to the liver and iiritant to the skin if used in substantial amounts or for too long a time. A number of phenols appear in essential oils as phenolic ethers. These are more complicated structures and have various word forms as seen in the following examples: safrole, methyl chavicol, eugenol methyl ether and asarone. Some phenolic ethers occur in two forms, as in trans-anethole and cis-anethole, the latter being the more toxic of the two. Phenolic ethers have some similar therapeutic effects to phenols, but, being more powerful, several may be neurotoxic if present in large amounts in an essential oil, thus indicating short term use in low concentration.

Ethers rarely, if ever, occur alone in essential oils. The relationship to phenolic ethers is close, their antidepressant, antispasmodic and sedative properties echoing those of the phenolic ethers, as do those of esters.


Antiviral, antiinflammatory, calming to the nervous system, hypotensors, vasodillators and antipyretic; their negative properties-when used incorrectly or inappropriately- can cause skin irritation and skin sensitivity.


Cicatrizant, lipolytic, mucolytic and sedative, some are also analgesic, anticoagulant or stimulant. They need to be used with care particularly by pregnant women.

Organic acids and esters

Antifungal, antiinflammatory, antispasmodic, cicatrizant and both calming and tonic, especially to the nervous system. Like alcohol, they are gentle in action, and being free from toxicity they are "user- friendly". The execption is methyl salicylate which comprises over 90 % of wintergreen and birch oils (neither of which are used in the present British style of aromatherapy).


The only known well in aromatherapy is 1,8 cineole, otherwise known as eucalyptol; it may also be regarded as a bicyclic ether. Eucalyptol is expectorant and mucolytic, its inwanted effect being skin irritation, especially on young children.


They occur only in the expressed oils and some absolutes, e.g. jasmine, because the molecular weight is too great to alow distillation. Lactones are reputed to be mucolytic, expectorant and temperature-reducing, their negative aspects being skin-sensitizing and phototoxicity.

Coumarines and forocoumarines

Coumarins are anticoagulant hypotensors, they are also uplifting and yet sedative. Furocoumarines are known mainly for their phototoxicity, and oils containing these should not be used immediatly prior to sunbathing (or sunbeds) due to their ability to increase the sensitivity of the skin to the sun. Some are antiviral and and antifungal.

Texts based on the books of:

-Franchomme and Dr Penoel

"L'aromatherapie exactement-Encyclopedie de l'utilisation therapeutique des huiles essentielles

Roger Jollois Editeur 1990

51, Rue Montmailler-87000 Limoges

ISBN: 2-87819-001-7

This is a major work, explaining very largely the chemotypes, all the components of essential oils and their medical action, covering about 250 essential oils.

Shirley Price:

Aromatherapy for Health Professionals, with a preface from Daniel Penoel, it is the first english book I saw with the french medical research clearly explained and very complete, although it covers only 55 essential oils, the most important ones I suppose. Aromatherapy for Health Professionals 1995

Shirley Price

Len Price

Foreword by Dr Daniel Penoel

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