Benzoyl Peroxide

Benzoyl peroxide (BPO) is an antibacterial and keratolytic agent used primarily to treat acne vulgaris. Unlike antibiotics, BPO kills acne-causing bacteria (C. acnes) through oxidation — bacteria cannot develop resistance to this mechanism, making it a long-term sustainable treatment.

Benzoyl peroxide works through three mechanisms: 1. **Antibacterial** – Releases oxygen radicals that destroy C. acnes bacteria. 2. **Keratolytic** – Helps shed dead skin cells and unclog pores. 3. **Anti-inflammatory** – Reduces redness and swelling in active breakouts. Unlike antibiotics, bacteria cannot develop resistance to BPO.

• **Wash/cleanser** – 2.5%–5%: Good for mild acne, leave on for 30–60 seconds. • **Leave-on gel/cream** – 2.5%–10%: More effective for moderate acne. • **Spot treatment** – 5%–10%: Apply directly to individual pimples. • Higher concentration does NOT mean faster results — 2.5% is as effective as 10% with less irritation.

• Start with a wash-off formula (2.5%) every other day. • If tolerated, increase to daily use after 2 weeks. • Apply leave-on products to completely dry skin to minimise irritation. • Use a pea-sized amount for the whole face. • Always moisturise after — BPO is drying. • Use SPF 50+ — BPO increases photosensitivity.

• **Bleaches fabric** – BPO will bleach towels, pillowcases, and clothing. Use white towels and bedding. • **Can cause initial purging** – Breakouts may worsen in the first 2–4 weeks before improving. • **Do not combine with retinoids in the same routine** – They cancel each other out. • **Can be drying** – Start slow and use a good moisturiser. • **Allergic reactions are rare but possible** – Discontinue if severe redness or swelling occurs.

Understanding when benzoyl peroxide is the right choice versus its alternatives: Benzoyl Peroxide (BPO): Best for inflamed acne (papules, pustules), acne driven primarily by C. acnes bacteria. Bacteria cannot develop resistance to BPO — a crucial advantage over antibiotics. Can be drying and irritating, bleaches fabrics. Evidence: multiple meta-analyses confirm BPO 2.5% is as effective as 5% or 10% with significantly less irritation. Salicylic Acid (BHA): Best for blackheads, whiteheads, congested pores, oily skin acne prevention. Oil-soluble — penetrates into follicles to dissolve sebum. Less effective against active inflamed pustules. Combination approach: Many dermatologists recommend alternating — BPO in AM (or spot-treating), BHA in PM. Do not apply both simultaneously — BPO oxidises BHA. Topical antibiotics (clindamycin, erythromycin): Best for inflammatory acne not responding to OTC options. Available by prescription only. Major limitation: antibiotic resistance. Always combine with BPO to reduce resistance development — a 2003 review in the Journal of Antimicrobial Chemotherapy showed BPO prevents resistance when combined with antibiotics. Retinoids (tretinoin, adapalene): Best for comedonal acne, long-term acne prevention, post-acne pigmentation. Do not use same night as BPO — they degrade each other.