Impact of preservatives in topicals on the cutaneous microbiota

Abstract

Preservatives are used to stabilize topical preparations and protect the user from the influence of pathogenic microbes. After the application of atopical preparation, the matrix undergoes ametamorphosis, and by proportional evaporation of the hydrophilic phase the preservative may accumulate on the skin surface. This is believed to lead to antiseptic effects and may influence the diversity of the cutaneous microbiota. The regulation of the cutaneous microbiome and the associated influencing factors is acomplex system that results in highly individualized conditions. Therefore, investigations on the influence of defined interventions are methodologically difficult. In the present proof-of-concept study, potential antiseptic effects of preservatives were investigated in acombination of in vitro and in vivo methods using microbiological culture tests. In addition, the investigations served to develop aclinical study design to answer further questions and use of an extended range of methods. The results support the hypothesis of an antiseptic effect of the tested preservatives (methyl-4-hydroxybenzoate and propyl-4-hydroxybenzoate, potassium sorbate and propylene glycol) on prominent reference bacteria, which could also be observed in clinical settings.