Carcinogens show comedogenic activity: a potential animal screen for tumorigenic substances

Formation of a comedo, an impaction of horny cells in sebaceous follicles, entails a metaplastic change in the differentiation patterns of the follicular epithelium. Since metaplasia is a requisite early stage in carcinogenesis, we postulated that carcinogens might be comedogenic. The rabbit ear was used to assay the comedogenic potentialities of an array of known tumorigens. Complete carcinogens and some tumor promotors were invariably strongly comedogenic at concentrations of 1.0% and below. Comedogenic chemicals commonly found in skin care products usually required concentrations of 40% and greater to induce comedones which were small in comparison to carcinogen induced comedones. We suggest that the rabbit ear model might be an easy and reliable way to screen for carcinogenicity.