Fragrance compounds and essential oils have been known since ancient times for their healing properties. Nearly all cultures had the knowledge of fumigating sick persons. Aromatic plants were used for their pleasant or invigorating odors to freshen sick rooms. And we are vey familiar with the word perfume which is derived from the Latin per fumum. The historical uses of fragrances in medicine have been reviewed by the author recently, therefore a repetition here is not necessary.
Nevertheless it is worth noting that essential oils are very heterogeneous mixtures of single substances—presently we have identified more than 3,000 compounds. Hence one has to be aware that biological actions are primarily due to these single substances in a very complicated concert of synergistic or antagonistic activities. Essential oils are not “the soul of the plant,” as someone has called this group of phytochemicals romantically, but totally unscientifically. These are chemicals created by nature with all the benefits and disadvantages that a chemical substance possesses. Mixtures of such chemicals therefore show a broad spectrum of biological effects.
This article will deal mainly with the mode of action of essential oils and fragrances. It is also necessary to express an opinion on the dispute over whether the observed effects are generated only by a pleasant feeling that is via a reflectorial way, or by a direct molecular interaction of the fragrance molecule with a receptor.