Challenge of preserving cosmetics

Since many cosmetic products cannot be sterile-manufactured or packaged, preservative systems are required. The first purpose of a preservation system is to inhibit microbial growth that leads to product spoilage. The second purpose is to protect the consumer from infection risks. In Europe, the importance of preservation is emphasised with the recommendation of setting a date of durability for the product. According to the Article 6(1) (c) of the Cosmetic Directive (76/768/EEC) the period of time after opening shall be indicated for all the products which are not single-use products or that cannot lead in case of deterioration to damage to human health according to Article 2 of the same directive. The expiry date of a product is obviously influenced by the preservatives used in the formulation.1 An adequate preservation system must also prevent, as a third purpose, the re-contamination of the product during its usage and the possible cross contamination among users. Other factors, for example the desire for “green” or natural products, also impact the type of preservative system that is used.

Hurdle technology

Besides adding a preservative to a product, a different type of preservation technique, called “hurdle technology”, can be utilised to aid in the preservation of a product.2 Hurdle technologies involve controlling the physical characteristics of the product. An example of a hurdle technology formulated to achieve a low water activity or low pH may help control microbial growth. Utilising hurdle technologies may also enable a formulator to decrease the amount of traditional preservatives needed to achieve microbiological control. The use of traditional preservatives in personal care products has been challenged in recent years, which has led to extensive research for natural preservatives.3 This natural trend observed in the market motivated the development of a new classification of preservatives into traditional and green preservatives. The traditional classification of preservatives follows their chemical characteristics (alcohols, parabens, phenols, quaternary ammonium salts, organic acids, biguanides). All traditional preservatives allowed for the use in personal care products are listed on the Annex VI part 1 or 2 of the EEC Cosmetic Directive 76/768/EEC – including the 7th amending Commission Directive 94/32/EC.1 These traditional preservatives stand opposed to the so-called “green” preservatives. Green preservatives are often considered to be natural substances that can improve the preservative characteristics of a formulation, but they are not considered as preservatives because they are not listed on Annex Vl. Examples of such substances would be certain plant-derived fragrances, emulsifiers, chelating agents and antioxidants.4 Preserving a product using only natural preserving ingredients not listed in the Cosmetic Directive allows the declaration of “preservative-free”. As a consequence, not all natural preserving ingredients are declared as preservatives under EU regulation. This means that, by definition, there are no all-natural preservatives on the market so far.