The therapeutic use of essential oils (EOs) and/or hydrolats has a long tradition. Nowadays the pharmacological and/or psychological properties of odorants are acknowledged and in many cases the combination of both play an important role. EOs are used as an adjunct in school medicine, folk medicine, Chinese medicine, alternative medicine, aromatherapy and massages, as well as in the cosmetics and perfumes industries, and in food flavourings and cleaning products.
A great number of studies exist which refer to the effects of EOs on the central nervous system (CNS), also several biological properties such as peripheral antinociceptive effects, anticancer effects, antiphlogistic effects, antiviral activity, and antioxidative activity.
Activities of EOs on the CNS have been extensively studied, such as analgesic effects, anxiolytic effects, effects on the treatment of stress, effects on learning, memory, attention and arousal, effects on relaxation, sedation and sleep, effects on mood, behaviour and perception, anticonvulsive effects and the treatment of epilepsy. The components of the EOs were often analysed and the mechanisms of action were assessed.
Not only the EOs in their entirety are responsible for the potency, but also single fragrance compounds (e.g. linalool as the main constituent of lavender), exert many effects. The studies mentioned prove that EOs can, apart from the autonomic nervous system, also influence the CNS, even if expectancies or the mental state sometimes play an important part.