What causes acne vulgaris?

The exact causes of acne vulgaris are not yet clear. Genetics may be the main factor. Other possible causes include hormones, infections, diet, and stress. Studies investigating the effects of smoking, sunlight exposure, and general hygiene have been inconclusive.

In contrast, the development of acne vulgaris on a cellular level is better understood. The pathogenesis of acne vulgaris revolves around four key factors:^[1]

1. Excess sebum production
2. Overgrowth of Cutibacterium acnes, the main bacterial species infecting clogged hair follicles
3. Hyperkeratinization, or excessive production of keratin, is one of the main structural proteins that stick skin cells together
4. Inflammatory processes