Since the middle ages, essential oils have been widely used for bactericidal, virucidal,
fungicidal, antiparasitical, insecticidal, medicinal and cosmetic applications, especially
nowadays in pharmaceutical, sanitary, cosmetic, agricultural and food industries.
Because of the mode of extraction, mostly by distillation from aromatic plants, they
contain a variety of volatile molecules such as terpenes and terpenoids, phenol-derived
aromatic components and aliphatic components. In vitro physicochemical assays characterise
most of them as antioxidants. However, recent work shows that in eukaryotic cells,
essential oils can act as prooxidants affecting inner cell membranes and organelles
such as mitochondria. Depending on type and concentration, they exhibit cytotoxic
effects on living cells but are usually non-genotoxic. In some cases, changes in intracellular
redox potential and mitochondrial dysfunction induced by essential oils can be associated
with their capacity to exert antigenotoxic effects. These findings suggest that, at
least in part, the encountered beneficial effects of essential oils are due to prooxidant
effects on the cellular level.