Common acne (Acne vulgaris) has 4 causes, which are often interconnected:
1. Too much sebum, an oily substance that lubricates the hairs that push through the surface of your skin. Hormones and genetics can influence the amount of sebum produced inside your hair follicles. When your sebaceous (oil) glands produce too much sebum, it can make your dead skin cells stick together and block your pores.
2. Too much bacteria called Cutibacterium acnes (C. acnes) in the pores. These bacteria love to feed on sebum.
3. Too many skin cells called keratinocytes and their output, keratin, which block pores through hyperkeratinization, when dead skin cells collect on the surface of the skin
4. Local inflammation, which may be related to a loss of bacterial diversity in the skin's microbiome
Different acne medications can target different acne causes. For example, benzoyl peroxide acne cream can kill C. acnes, reduce inflammation, and help the skin shed dead cells. Retinoids like tretinoin (Retin-A) can help normalize sebum production and unblock pores.
Clinicians often prescribe a combination of acne medications for the best results.