The daily application of human sebum for two weeks to the external canal of the rabbit ear induced the following histologic changes: (1) hyperplasia of the epidermis and epithelial linings of the sebaceous ducts and follicles, (2) distention of the ducts and follicles with keratinized squamae to form horny impactions or comedones, and (3) variable inflammatory changes exemplified by follicular pustules and infiltration of the dermis by mononuclears and polymorphonuclear leukocytes.
The comedogenic potency of sebum is considerably less than that of a chemical acneigen such as Halowax 1014. The comedones were smaller and never attained maturity.
Kligman AM. Pathogenesis of Acne VulgarisII. Histopathology of Comedones Induced in the Rabbit Ear by Human Sebum. Arch Dermatol. 1968;98(1):58-66. doi:10.1001/archderm.1968.01610130064014