Aromatherapy is derived from two words, aroma, meaning fragrance or smell and therapy, meaning treatment. Aromatherapy was used by almost every ancient civilization and is thought to be at least 4,000 years old, beginning in Egypt. Rene-Maurice Gattefosse, a French chemist working in his family's perfumier business, first coined the term "aromatherapy" in 1928. He became fascinated with the therapeutic possibilities of the oils after discovering by accident that lavender was able to heal a severe burn on his hand quite rapidly and help prevent scarring. In 1904 Cuthbert Hall had shown that the antiseptic power of eucalyptus oil in its natural form was stronger than its isolated main active constituent, "eucalyptol" or "cineol". A French doctor and scientist, Dr. Jean Valnet, used essential oils as part of a program by which he successfully treated specific medical and psychiatric disorders.

Therefore it is important to recognize that essential oils have three distinct modes of action with regard to how they interrelate with the human body: pharmacological, physiological and psychological. The pharmacological effect is concerned with the chemical changes that take place when an essential oil enters the bloodstream and reacts with the hormones and enzymes, etc.; the physiological mode with the way in which an essential oil affects the system of the body, whether they are sedated or stimulated, etc.; the psychological effect takes place when an essence is inhaled, and an individual responds to it odor. On the first two points, aromatherapy has much in common with the tradition of medical herbalism or phytotherapy - in other words, it is not simply the aroma that is important but also the chemical interaction between the oils and the body, and the physical changes that are brought about.