Antimicrobial stabilisation of cosmetic products

Currently, the number of accepted substances for microbial stabilisation is limited due to legal restrictions or public discussion. Hurdle technology and the intelligent combination of multifunctional additives help to design microbiologically stable products. The synergistic blend of phenethyl alcohol and ethylhexylglycerin is an effective stabilisation system, while consisting of 90% nature-identical material.

 The regulatory framework for preservatives varies in different regions. According to the EU Cosmetics Directive 76/768/EEC preservatives are substances ‘for the primary purpose of inhibiting the development of microorganisms’ in cosmetic products. These substances are listed in Annex VI of the EU Cosmetics Directive.1 Japan lists preservatives in Annex III of the Japanese Standard of Cosmetics.2 Under the Federal Food, Drug, and Cosmetic Act in the US, cosmetic ingredients, with the exception of colour additives, ‘do not require FDA approval before they go on the market. Companies who market cosmetics have the legal responsibility to ensure the safety of their products’.3 In addition to legal requirements, the options for microbial stabilisation are restricted by marketing demands. The movement to preservative-free or natural products and restrictions on certain actives, i.e. formaldehyde-releasers, isothiazolinones, etc., are increasing. The desire to avoid cosmetic preservatives extends to all categories of traditional preservatives, leading to a limited number of accepted actives. Parabens, for example, are some of the most commonly used preservatives due to their excellent efficacy and low sensitising potential.4,5 Public discussion has caused some manufacturers to avoid using these materials in new formulations. The claim ‘paraben-free’ on personal care products first appeared in 2005. According to market research company Mintel, in 2011 this claim was used for 9% of total beauty and personal care launches worldwide; mainly in North America, Europe, and Japan. In contrast, the ‘preservative-free’ claim is still of minor importance. Less than one per cent of new cosmetic products were launched worldwide with this claim; mainly in Japan (3% of total launches).6 It is debatable whether these claims meet the consumer needs or increase their uncertainty of the safety of cosmetic products. In addition, the trend to natural and sustainable products is ongoing. According to Kline & Company, the global natural personal care segment in 2010 is about USD 23 bn. This is a small segment in the personal care market (~USD 300 bn). However, the sales growth of 15% from 2009 to 2010 and the expected annual sales growth of 12% through 2015 are remarkable.7,8 There is still no universal definition of ‘natural’ within the personal care market. Looking into the ingredients of natural products, Kline differs in ‘truly natural’ and ‘natural-inspired’ products and states that 76% of global sales of natural products are in the group of ‘natural-inspired’. The majority of ingredients in naturalinspired products are synthetic. These are combined with some natural ingredients. The ‘truly natural’ criteria often include higher portions of natural ingredients and mainly avoid less desirable ingredients such as silicones, ethoxylates, chemical UV filters, and synthetic preservatives.7 However, products including high percentages of natural components are more susceptible to microbial contamination, either because the raw material contains a high initial bio-burden or because most natural materials are an excellent medium for microbial growth. Due to these obstacles, formulators are interested in finding novel ways to keep cosmetic products microbiologically stable.

Technologies in use