Acne

Acne is a disorder of the pilosebaceous unit: increased sebum, abnormal keratinisation blocking the follicle, Cutibacterium acnes proliferation, and inflammation. Treatments target those steps, and the herbal options are a weak version of the standard ones.

What has the best evidence. Topical retinoids (tretinoin, adapalene) — the treatment that actually changes the disease, and available over the counter in some countries as adapalene. Benzoyl peroxide for the antibacterial and keratolytic effect. Oral antibiotics and hormonal treatments for moderate to severe cases. Isotretinoin for severe or scarring acne. A person with scarring acne should see a dermatologist, because scarring is permanent and the window to prevent it is now.

Tea tree oil at 5% has a randomised trial showing effectiveness roughly comparable to 5% benzoyl peroxide with fewer side effects and a slower onset (allow 8-12 weeks). It is a reasonable option for mild acne in someone who tolerates benzoyl peroxide badly or prefers a plant product.

Niacinamide at 4% has small trials showing benefit and it is well tolerated. Green tea extract and azelaic acid (a dicarboxylic acid originally from grain, now synthesised) have evidence; azelaic acid is a genuine effective treatment for both acne and rosacea.

What does not work and is sold anyway. Most "herbal acne" blends; scrubbing (which worsens it); alcohol-based toners (irritant); and the various "detox" claims. Diet: a high glycaemic-index diet and, for some people, dairy, are associated with acne in observational and small interventional studies; the evidence is moderate and worth a trial in someone with persistent acne.

What people get wrong. Stopping treatment as soon as the skin clears, which is what brings it back. Topical retinoids cause an initial flare and irritation in the first weeks and people abandon them just before they work. And picking at lesions, which causes the scars that matter.