A large variety of microorganisms such as Propionibacterium acnes and Staphlococcus epidermidis exist on the human skin surface, forming a skin microbial flora. This flora is likely to influence the skin surface defence and the skin surface condition. This report covers the correlation between the skin microbial flora and the skin surface condition.
We found that the larger numbers of P. acnes are concerned in the worsening of skin surface condition. The skin condition closely correlated to the amount of free fatty acids on the skin, and also we found that the larger quantity of the free fatty acids leads the worsening of skin surface condition. These results suggest that the lipase of P. acnes may hydrolyze triglycerides on the skin surface into the free fatty acids which irritate the skin.
On the other hand, we found that both S. epidermidis itself and the peptides produced from various proteins by S. epidermidis have high antioxidative activity. This result suggests that S. epidermidis protects the lipids on the skin from oxidation caused by e. g. ultraviolet rays.
From these results we suggest that P. acnes make worse the skin surface condition, whereas S. epidermidis serves an important function of prevention of the worsening of the skin condition by harmful lipids peroxides.
