Developing new cosmetic formulations by replacing chemical preservatives with ingredients with antimicrobial properties not legislated as preservatives is a key route to developing preservative-free or self-preserving cosmetics.

Microbial spoilage of cosmetic formulations has always been of special concern for the industry since it can lead to product degradation. Chemical preservatives are added to cosmetics to protect them against microbial contamination.

A recent trend is the replacement of traditional chemical preservatives with antimicrobial agents that are not legislated as preservatives according to Annex VI of Commission Directive 1976/768/EEC (3-5) but that are safe and effective as preservatives.

An approach to achieving preservative-free cosmetics is the selection of natural compounds that have been characterized as safe and effective against microorganisms, in order to decrease or eliminate the use of the traditional chemical preservatives.

A number of plant-derived essential oils and extracts exhibit excellent antimicrobial properties and have been used for the effective preservation of cosmetic formulations. Among others, derivatives of Rosmarinus officinalis, Lavandula officinalis, Thymus vulgaris and Eucalyptus globulus are effective natural preservatives.

Medium polar substances are also alternative antimicrobial agents. Caprylyl glycol and monoglycerides of capric acid and caprylic acid, besides being moisturizing agents, exert antimicrobial activities. Due to their emulsifier-like structure, they interfere with the cellular structures of microorganisms and disintegrate cell membranes.

The chemical composition of fragrances plays a key role in the antimicrobial activity of essential oils and extracts obtained from natural sources. Various aldehydes and alcohols are among the most active compounds. In the past, a fragrance mixture consisting of benzyl acetate, phenethyl alcohol and linalool had been proposed as an alternative preservative. Today several antimicrobial fragrance ingredients are commercially available, such as p-anisic acid (p-methoxy-benzoic acid) and levulinic acid (4-oxo-pentanoic acid).

So, what do you use as a preservative now?