ConditionsIngredientsProceduresMedications
Ingredient

Benzoyl peroxide

Also called BP or BPO
Reviewed by Dr. Schwarz, Board Certified Dermatologist
At a Glance

Benzoyl peroxide is the main over-the-counter treatment for red, inflamed acne. It works by releasing oxygen into the pore, which kills the bacteria involved in acne.

Because it is not an antibiotic, bacteria do not become resistant to it. That is why it is often paired with antibiotics rather than replacing them.

Key facts

Also calledBP, BPO
Typical strength2.5%, 5% or 10%
Best forRed, inflamed pimples
OTC or prescriptionOver the counter; also in prescription combinations
Time to see results6–8 weeks, up to 3 months for full effect

How it works

Benzoyl peroxide breaks down on the skin and releases oxygen into the pore. The bacteria involved in acne cannot survive in that environment. It also loosens the clog slightly and reduces the oil in the follicle.

Antibiotics work by blocking one specific process inside a bacterium, so a single mutation can defeat them. Benzoyl peroxide damages many parts of the bacterium at once by simple chemistry, the way bleach does. There is no single thing for bacteria to adapt to, which is why resistance has not developed to it.

What it treats

Over the counter
Benzoyl peroxideStrong evidence
The main over-the-counter treatment for red, inflamed acne.

Side effects

Nearly all of these are irritation, and nearly all settle if you use it less often at first.

Common and expected
  • Dryness, peeling and redness, especially in the first two weeks.
  • Stinging on application.
  • Bleaching of anything it touches — towels, pillowcases, shirts, and coloured hair. This is permanent.
Tell your doctor
  • Irritation that does not settle after a few weeks of alternate-day use.
  • Skin that becomes itchy, swollen or blistered rather than just dry — this may be an allergy rather than irritation.
Stop and get care
  • Swelling of the face, lips or throat, faintness or difficulty breathing after applying it. This is rare but has been reported.
If it stings too much, wash it off after an hour at first, or use it every other day and build up. This is standard advice in the UK national acne guideline, not a workaround.

Everyday habits

Most people who say benzoyl peroxide did not work either stopped at week three or used it on top of already-irritated skin.

Getting started
  • Start slowEvery other day for the first week or two, then daily.
  • A pea-sized amountFor the whole face. More does not work better.
  • MoisturizeAfterwards, every time. It is what makes it tolerable.
Protect your things
  • White pillowcases and towelsThe bleaching is permanent and cannot be washed out.
  • Let it dryBefore you dress or get into bed.
  • Wash your handsIt will lighten dyed hair, eyebrows and beards.
Give it time
  • Six to eight weeksBefore you judge whether it is working.
  • Keep going after it clearsIt treats the conditions that make spots, not the spots you already have.
  • Store it coolNot in a hot car or a steamy bathroom.
What the research says1 studies+
1 in 2
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Common myths+
Benzoyl peroxide destroys tretinoin, so they can never be used together.This comes from a 1998 lab test that mixed 10% benzoyl peroxide with an old tretinoin formulation under bright light. Newer testing found no degradation at all over seven hours at skin temperature, and the FDA has since approved a single cream containing both. Using one in the morning and one at night is a free precaution, but the blanket claim overstates the evidence.
Acne always purges on benzoyl peroxide for two to six weeks.No authoritative source describes a purging phase for benzoyl peroxide. What is well documented is early dryness, redness and peeling — irritation, not more spots. The purge timeline circulates on skincare blogs and traces to no study.
10% works better than 2.5%.The head-to-head evidence does not support it. Higher strengths reliably irritate more.
Benzoyl peroxide products cause cancer because of benzene.An independent lab reported benzene in benzoyl peroxide products in March 2024, mostly after heating them. The FDA then tested 95 products as sold: more than 90% had undetectable or extremely low levels, six were recalled, and the FDA stated the cancer risk even with decades of daily use is very low. The practical takeaway is about storage — keep it cool, replace it every few months.
Who should be careful+

Benzoyl peroxide suits most people, but go carefully if you have:

Very dry or eczema-prone skin. Start with a wash rather than a leave-on gel.

A lot of other active products in your routine. Layering benzoyl peroxide over acids or a retinoid on the same skin is the usual cause of severe irritation.

Darker skin. Irritation can leave dark marks that outlast the spot, so it is worth building up slowly.

Questions people ask+
Wash or leave-on gel?A wash is gentler and easier for the chest and back; leave it on two to five minutes before rinsing. Leave-on gel is what almost every trial used, so it has the stronger evidence.
Can I use it with a retinoid?Yes. Guidelines recommend the combination, and fixed-dose products exist. If you are worried about irritation, use one in the morning and one at night.
Will bacteria become resistant?No. It is not an antibiotic. This is exactly why it is added to antibiotic treatment.
How long before it works?Six to eight weeks for a visible difference, three to four months for full effect.
Can I use it forever?Yes. There is no resistance and no known limit on length of use.
References+

1. Cochrane — topical benzoyl peroxide for acne, 2020 (120 trials, 29,592 participants). 2. American Academy of Dermatology — guidelines of care for the management of acne vulgaris, 2024. 3. NICE NG198 — acne vulgaris: management. 4. FDA — testing of acne products for benzene, March 2025.

Full citations and links are added as each claim on this page is checked.