blackhead

A blackhead, also known as an open comedo, is a small plug of darkened sebum and dead skin cells that fills a pore on the skin, most commonly on the face. This is a hallmark of acne vulgaris, a common skin condition affecting adolescents.12

Acne occurs in the pilosebaceous unit, which includes the hair follicle and the sebaceous gland that produces sebum, an oily substance. Sebum production increases significantly during puberty. When keratinous debris and sebum accumulate in the pilosebaceous duct, it forms a comedo. If this plug is exposed to air, it oxidizes and darkens, appearing as a blackhead. Acne can also present as inflamed papules, pustules, and cysts, sometimes exacerbated by bacteria like Propionibacterium acnes.21