Cosmetics: what is their influence on the skin microflora?

Human skin has a resident, transient and temporary resident microflora. This article considers the possibilities of topical products influencing the balance of the microflora. The resident micro-organisms are in a dynamic equilibrium with the host tissue and the microflora may be considered an integral component of the normal human skin. The great majority of these micro-organisms are gram-positive and reside on the skin surface and in the follicles. The host has a variety of structures, molecules and mechanisms which restrict the transient and temporary residents, as well as controlling the population and dominance of the resident group. These include local skin anatomy, hydration, nutrients and inhibitors of various types. The resident microflora is beneficial in occupying a niche and denying its access to transients, which may be harmful and infectious. Also, the residents are important in modifying the immune system. In the healthy host the microflora causes few and temporary problems. Therefore, it is of interest that topical products have little or no effect on the ecology of the microflora. A range of mechanisms by which long-term use of cosmetics may influence the microflora are considered. Although the risks associated are low, it is argued that it is necessary to monitor these changes in ecology and use technologies of modeling and bioinformatics to predict outcomes, whether good, neutral or of concern.