Comedogenicity and irritancy of commonly used ingredients in skin care products

A survey, using the rabbit ear, of the comedogenicity and irritancy of several groups of skin care products indicates that many contain follicular and surface pithelial irritating ingredients. These ingredients fall into several chemical classes. Certain generalizations can be deduced by examining the results: (1) medium-chain-length fatty acids are more potent than shortor long-chain fatty acids in producing follicular keratosis, (2) the comedogenicity and irritancy of an organic material can be reduced by combining the molecule with a polar sugar or a heavy metal, (3) increasing the degree of ethoxylation in a molecule tends to reduce the comedogenicity and irritancy of the chemical, and (4) the longer chain lipids, i.e., waxes, appear too large to produce a reaction. By following the guidelines developed in this study, it is possible to formulate nonirritating, noncomedogenic moisturizers, sunscreens, hair pomades, cosmetics, and conditioners.