Comparison of objective and sensory skin irritations of several cosmetic preservatives

There are many cosmetic ingredients, such as preservatives and fragrances, known to elicit adverse effects. The aim of this study was to investigate the side-effects of cosmetic preservatives, by evaluating objective and subjective skin irritation. The method comprised of 2 parts. In part 1, we tried to compare 24-hr patch test results with the sensory irritation potential of several preservatives. In part 2, skin cumulative irritation test for 21 days and sensory irritation test were performed to compare various combinations of preservatives in 4 types of formulations. Our data showed that methylparaben, ethylparaben, propylparaben, butylparaben, phenoxyethanol (PE) and chlorphenesin (CPN) have similar objective skin irritation potential at the minimal inhibitory concentration of each preservative, but CPN has higher potential than other preservatives in subjective irritation. Sensory irritation of preservatives changed according to formulation type, and PE combined with CPN highly increased irritation. There was correlation between antimicrobial activity and skin objective irritation but not sensory irritation. Influence on skin sensory irritation varies with the combination of preservatives. Therefore, for the development of new preservatives and cosmetics, it is important to evaluate skin sensory irritation of preservatives used in cosmetic products according to the type of formulations.