What Causes Acne
Acne (acne vulgaris) is a multifactorial skin condition involving four primary mechanisms:
- Excess sebum production — influenced by hormonal activity (particularly androgens), genetics, and stress
- Abnormal skin cell shedding — dead skin cells that are not shed normally can block follicles
- Bacterial proliferation — Cutibacterium acnes (formerly Propionibacterium acnes) is normally present on skin but proliferates in blocked follicles, triggering inflammation
- Inflammation — immune response to bacteria and follicular rupture creates inflammatory lesions
Hormonal influences are significant, particularly in adolescence, around menstrual cycles, and in conditions like polycystic ovary syndrome (PCOS). Genetics plays a major role in predisposition. The common belief that diet causes acne is supported by some evidence — particularly around high-glycaemic-index foods and dairy — though the effect size varies between individuals.
Types of Acne Lesions
Understanding acne lesion types helps identify appropriate treatments:
| Lesion Type | Description | Best Treatment Approach |
|---|---|---|
| Comedones (open) | Blackheads — oxidised debris visible at surface | BHA (salicylic acid), retinoids |
| Comedones (closed) | Whiteheads — blocked follicles below surface | Retinoids, AHAs, BHAs |
| Papules | Small, raised, red, tender bumps | Benzoyl peroxide, retinoids, niacinamide |
| Pustules | Papules with visible white/yellow pus | Benzoyl peroxide, topical antibiotics (with caution) |
| Nodules / Cysts | Deep, painful, large; risk of scarring | Dermatologist referral — may require isotretinoin or prescription oral treatment |
Evidence-Based Treatments
Acne treatments are ranked by evidence strength. In rough order of overall evidence quality for most acne types:
- Retinoids (topical) — first-line treatment in most dermatology guidelines for comedonal and mild-moderate inflammatory acne. Tretinoin, adapalene, and OTC retinol all have evidence.
- Benzoyl peroxide — effective against C. acnes, reduces inflammation, does not cause antibiotic resistance. A cornerstone of acne treatment for over 50 years.
- Salicylic acid (BHA) — exfoliates inside the follicle, reduces comedones. Lower evidence level than above but practical and well-tolerated OTC option.
- Topical antibiotics — typically prescription-only; effective short-term but antibiotic resistance is a concern with long-term use. Usually combined with benzoyl peroxide for this reason.
- Oral isotretinoin (Accutane) — for severe, nodular, or scarring acne. Highly effective but requires medical supervision and monitoring due to side effect profile.
Key Ingredients
Oil-soluble; penetrates follicles; exfoliates inside the pore. Effective for blackheads, whiteheads, and mild inflammatory acne. 0.5–2% concentration. Avoid overuse — can be drying.
Kills acne-causing bacteria without promoting resistance. Available OTC at 2.5–10%. Studies show 2.5% is as effective as higher concentrations with less irritation. Can bleach fabrics.
For a full skincare routine approach that incorporates acne treatment, see our skincare routine guide.
Lifestyle Factors
Several lifestyle factors influence acne, with varying levels of evidence:
- Diet (moderate evidence) — high glycaemic index diets and dairy (particularly skimmed milk) are associated with worse acne in some studies. A Mediterranean-style diet is associated with lower acne severity in some research. Individual responses vary considerably.
- Stress (moderate evidence) — stress increases cortisol and androgens, which stimulate sebum production. Stress management supports skin health broadly. See our sleep and skin guide.
- Pillowcase hygiene — changing pillowcases 2× per week reduces bacterial transfer to facial skin; low evidence individually but rational practice.
- Phone hygiene — phones harbour significant bacteria; keeping them clean and away from the face reduces bacterial exposure.
When to See a Dermatologist
Seek dermatologist assessment when: OTC treatments have not produced improvement after 12 weeks of consistent use; acne is causing or at risk of causing scarring; acne is significantly affecting mental health or quality of life; nodular or cystic lesions are present; acne is severe or worsening despite appropriate treatment.
In the UK, you can be referred by your GP to a dermatologist on the NHS. Private dermatology appointments are available in most areas. Early treatment of severe acne is important — acne scarring, once established, is significantly harder to treat than the acne itself.
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