ABSTRACT
In most cases, essential oils are safe in use except in overdosage, wrong application route, and in hypersensitive persons. Toxicity of essential oils is concentration-dependent, and thus most of unwanted side effects can be avoided by application of low doses and restriction to small skin areas. Hypersensitive people should avoid essential oils, because allergic reactions occur independently of the applied concentration and route of application. Adequate storage of essential oils is mandatory, because oxidation products formed by exposure to light and/or air may play an important role in toxicity. Most severe intoxications occur in children following accidental ingestion. Subjects of special concern are the epileptogenic effect of camphor-, eucalyptol-, and thujone-containing essential oils; severe hepatotoxicity of pennyroyal oil due to pulegone and menthofuran, and at high concentrations of clove oil due to eucalyptol; salicylate intoxication with wintergreen oil; phototoxicity of coumarin- and furocoumarin-containing bergamot oil; application in pregnant women because components of essential oils easily cross the placental barrier and may harm the fetus and neonates; and the use, particularly in infants and young children, as they are prone to severe intoxication.
