Application of essential oils as natural cosmetic preservatives

Nowadays, safety of chemical preservatives has been questioned by a big number of consumers. Traditionally used preservatives often cause skin irritation and lead to allergenic reactions. Growing demands for more natural and preservative-free cosmetics promoted an idea of the replacement of synthetic preservatives with essential oils (EOs) of antimicrobial properties. The antimicrobial effect of essential oil depends on content, concentration and interactions between the main active compounds. Effective preservatives should be characterized by a broad spectrum of antimicrobial activity at a minimum concentration. Formulations containing both types of preservatives: essential oil and a synthetic one have been tested and proposed as a compromise that allows for reducing concentration of both components due to their synergistic activity. Although most essential oils are regarded as safe, some of them may cause risk of contact allergy or phototoxic reaction. A well balanced risk-benefit assessment of essential oils is one of the great challenges for scientists or health policy authorities. This paper presents current state of knowledge on essential oils focused on their antimicrobial properties, the assessment of their efficacy and safety as cosmetic preservatives.