Benzoyl Peroxide
Also known as BPO
The antibacterial backbone of acne treatment, and the reason topical antibiotics still work.
$8–25 for OTC formulations.
How it works
Releases free radical oxygen into the follicle, killing C. acnes directly. Because the mechanism is oxidative rather than biochemical, bacteria do not develop resistance to it — which is why it is paired with antibiotics that they otherwise would.
How it's used
2.5% is as effective as higher strengths with far less irritation — start there. Use as a short-contact wash (apply, wait two minutes, rinse) if leave-on is too drying. Do not layer directly with tretinoin in the same application.
Trade-offs
In favour
- No bacterial resistance develops
- Cheap and available everywhere
- Prevents resistance when paired with topical antibiotics
- Fast-acting on inflammatory lesions
Against
- Bleaches fabric — towels, pillowcases, dark shirts
- Drying and irritating
- Does little for comedonal acne alone
Risks and side effects
- Contact dermatitis
- Fabric and hair bleaching
- Rare true allergy
How good is the evidence?
Long-standing randomised evidence and universal guideline inclusion.
Sources
Sources point to guideline bodies and literature searches rather than single papers, so they stay accurate as the evidence moves.