Benzoyl Peroxide

Benzoyl peroxide is the fastest-acting over-the-counter acne fighter: it releases free oxygen radicals into the follicle that kill anaerobic Cutibacterium acnes within days. At 2.5–10% it clears inflammatory pimples and, unlike antibiotics, has never generated clinically relevant bacterial resistance — which is why dermatology guidelines pair it with topical retinoids or antibiotics. Caveats: it is drying, bleaches fabrics and hair, and can irritate sensitive skin, so 2.5% is usually as effective as higher strengths with less damage. Apply as a thin layer to affected areas or use as a short contact cleanser. Combine cautiously with retinoids — adapalene is the most stable partner.