Antimicrobial Efficacy of Preservatives used in Skin Care Products on Skin Micro Biota

Bacteria are the dominant group of skin microbiota that colonize the human skin and protect from invasions. Variations in skin microbiota because of the use of skin care products containing preservatives have been studied by testing three organisms - Pseudomonas aeruginosa, Micrococcus luteus and Staphylococcus epidermidis against the six selected preservatives Phenoxyethanol, Methyl paraben, Propyl paraben, Sorbic acid, Potassium sorbate and Sodium benzoate. The Minimum Inhibitory concentrations of the six preservatives were determined followed by challenge tests and have shown desired results of Antimicrobial Efficacy in between 0.2, 0.3, 0.4, 0.5 & 0.6 percent concentrations by achieving 3 log reductions for 14 days & 7 log reductions at 21 days respectively. The study revealed that the combination of two or more preservatives at 0.1 % concentration was found to be more than the effect of single preservative at higher concentration. The behavior of the three organisms with the three acid preservatives Sorbic acid, Potassium sorbate and Sodium benzoate at pH 5.5 was examined. This indicated that lowering the pH of personal/skin care products will not only be beneficial for the control of microbial growth in the products but also bring down the pH of the skin to the recommended levels.