Benzoyl peroxide (BPO) 2.5% is an over‑the‑counter acne treatment with antibacterial, comedolytic, and mild anti‑inflammatory actions against Cutibacterium acnes and follicular blockage. Randomized trials show 2.5% can be as effective as 5–10% for inflammatory lesions, with generally better tolerability than higher strengths. It does not induce antibiotic resistance and is often combined with topical antibiotics to reduce resistance risk and enhance activity against resistant C. acnes strains. Adapalene remains chemically stable with BPO whereas tretinoin degrades rapidly when mixed with BPO under light, informing compatible regimen design.