Comedogenicity of current therapeutic products, cosmetics, and ingredients in the rabbit ear.

Cosmetics continue to be used by acne-prone individuals. Often as more acne develops, more cosmetics are applied. In order to protect against this natural tendency, physicians should provide more patient information on the currently available products and ingredients. This presentation is designed to help in that effort. The data presented were gleaned from the rabbit ear assay, which is not an ideal animal model but is the best we have. If an ingredient is negative in the rabbit ear assay, we feel it is safe on the acne-prone skin. A strong, positive ingredient or cosmetic should be avoided. Ingredient offenders include isopropyl myristate and its analogs, such as isopropyl palmitate, isopropyl isostearate, butyl stearate, isostearyl neopentanoate, myristyl myristate, decyl oleate, octyl stearate, octyl palmitate or isocetyl stearate, and new introductions by the cosmetic industry, such as propylene glycol-2 (PPG-2) myristyl propionate. Lanolins continue to be a problem, especially derivatives such as acetylated or ethoxylated lanolins. Our most troublesome recent finding is the comedogenic potential of the D & C Red dyes. They are universally used in the cosmetic industry, especially in blushers. This may explain the predominance of cosmetic acne in the cheekbone area. All of these D & C Red dyes tested to date, the xanthenes, monoazoanilines, fluorans, and indigoids, are comedogenic. Actually, this is not surprising as they are coal tar derivatives. The natural red pigment, carmine, is noncomedogenic and can serve as a substitute for D & C dyes in blushers. Many finished products are comedogenic. Most troublesome to the dermatologists are the therapeutic tools that we use, such as Liquimat, Retin-A cream, Hytone, Staticin, Sulfoxl, Desquam-X, and Persadox HP cream. These should be reformulated. We have been unable to confirm that precipitated sulfur (U.S.P.) is a potent comedogen in the rabbit ear assay. Clinically, we still find sulfur quite effective as an adjuvant to the benzoyl peroxide therapy for the treatment of acne vulgaris. We would suggest that the bias against sulfur be reconsidered.