Aromatherapists aim to use oils whose chemical composition are as near as possible to that which occurs in the plant. Any addition or removal of chemicals from the natural oil during the extraction process constitutes adulteration and can affect the therapeutic effectiveness.

In addition to adulteration the oil may be contaminated during growth and harvesting. Although sophisticated chemical testing is now available, essential oils are often such complicated mixtures of chemicals, that the level of testing required to completely establish purity would be prohibitively expensive. In America the Food and Drug Authority (F.D.A.) has responsibility for monitoring purity of oils but unfortunately there is no equivalent body in the U.K. However the International Organisation for Standards (I.S.O.) based in Bilbao in Spain does set international standards for quality of oils.

TYPES OF ADULTERATION    TYPES OF CONTAMINATION     TESTING OF OILS