Assessment of Comedogenicity of Cosmetics in Humans and Rabbits

Cosmetics that are moderately to strongly comedogenic in the rabbit ear model test have been found to be capable of inducing comedones in human model.

In humans the test cosmetics were applied under occlusion for 4 weeks to the scapular region of young adults. The degree of follicular hyperkeratosis was assessed by a noninvasive skin surface biopsy technique, employing a fast-setting cyanoacrylate adhesive to remove the follicular content.

The rabbit model was more sensitive than the human. The test materials were applied once every day for 2 weeks onto the ventral surface of ear just external to ear canal. Excised tissue was thus immeresd in water at 60℃ for 2 minutes, yielding a sheet of epidermis with microcomedones attached.

The magnitude of follicular hyperkeratosis was assessed under the stereomicroscope. High correlation between assay results of comedogenicity in humans and rabbits was found. So, it was concluded that rabbit ear assay is a simple and rapid method to assess the comedogenicity of cosmetics and other contactants.