A human model for assaying comedolytic substances

The comedolytic activity of topical medicaments may be quantitatively assessed by inducing microcomedones on the backs of black males by a 2-week occlusive exposure to 10% crude coal tar. The test agents are then applied for 2 weeks and the reduction in density of microcomedones is determined by the non-invasive ‘follicular biopsy’ technique using cyanoacrylate adhesive. Only two of the many agents that were tested demonstrated appreciable comedolytic activity, namely retinoic acid (tretinoin) and salicylic acid. The former was more potent in dosage response assays.