Pathophysiology[edit]
Hair follicle anatomy
Acne develops as a result of blockages in the follicles. The earliest pathologic changes are the excessive deposition of the protein keratin and oily sebum in the hair follicle resulting in the formation of a plug (a microcomedo).[6] During adrenarche, a higher level of the androgen (DHEA-S) results in the enlargement of the sebaceous glands and increases sebum production. A microcomedo may enlarge to form an open comedo (blackhead) or closed comedo. The dark color of a blackhead occurs due to oxidation of the skin pigment melanin.[12]
Comedones result from the clogging of sebaceous glands with sebum, a naturally occurring oil, and dead skin cells.[6] In these conditions, the naturally occurring largely commensal bacterium Propionibacterium acnes can cause inflammation within and around the follicle, leading to inflammatory lesions (papules, infected pustules, or nodules) in the dermis around the microcomedo or comedone, which results in redness and may result in scarring or hyperpigmentation.[6][42][43] Severe acne is inflammatory, but acne can also be noninflammatory