How Do Closed Comedones Form?

Closed comedones—commonly known as whiteheads—are non-inflammatory acne lesions that form when hair follicles become obstructed by a mixture of excess sebum and keratinized epithelial cells. Unlike open comedones (blackheads), closed comedones remain covered by a thin layer of epidermis, preventing oxidation of the trapped material and thus retaining a flesh-colored or whitish appearance.

The pathogenesis begins with abnormal keratinization in the pilosebaceous unit, particularly within the infundibulum—the upper portion of the hair follicle. This dyskeratosis leads to hyperproliferation and impaired desquamation of follicular keratinocytes, resulting in microcomedone formation. Concurrently, increased sebum production—often hormonally driven, especially by androgens—provides a lipid-rich environment that further promotes follicular plugging. Propionibacterium acnes (now reclassified as Cutibacterium acnes) is not directly involved in closed comedone formation, as these lesions lack inflammation; however, its proliferation in later stages may contribute to progression toward inflammatory acne.

Contributing factors include genetic predisposition, hormonal fluctuations (e.g., during puberty, menstruation, or polycystic ovary syndrome), use of comedogenic topical products (such as heavy oils or occlusive cosmetics), and certain medications like corticosteroids or lithium. Environmental influences—including high humidity and friction from masks or headgear—may also exacerbate follicular occlusion.

Management focuses on normalizing follicular keratinization and reducing sebum accumulation. First-line topical therapies include retinoids (e.g., tretinoin, adapalene), which modulate keratinocyte differentiation and promote comedolysis. Salicylic acid and azelaic acid serve as adjunctive agents with keratolytic and anti-inflammatory properties. In persistent or widespread cases, oral retinoids such as isotretinoin may be indicated under dermatologic supervision.