Benzoyl Peroxide
Antimicrobial agent effective in treating acne by killing acne-causing bacteria.
What is Benzoyl Peroxide?
CAS Number
94-36-0
Formula
C14H10O4
Molecular Weight
242.23 g/mol
Also known as: BPO, Dibenzoyl Peroxide
What does Benzoyl Peroxide do for skin?
Generates free radicals (benzoyloxyl and phenyl) that oxidize bacterial proteins in the pilosebaceous unit. Bactericidal against Cutibacterium acnes (reduces bacterial counts by 98% within 48 hours). Does not induce bacterial resistance (unlike topical antibiotics). Mild comedolytic and anti-inflammatory activity. Penetrates the follicular duct.
Typical concentration: 2.5-10% (OTC), prescription formulations vary
Is Benzoyl Peroxide safe?
FDA-approved OTC acne monograph ingredient. Common side effects: dryness, peeling, erythema. Bleaches fabrics and hair. Contact sensitization rate ~1-2%. 2.5% as effective as 10% with fewer side effects.
What does the research say about Benzoyl Peroxide?
2.5% benzoyl peroxide as effective as 10% with less irritation
Mills et al., International Journal of Dermatology, 1986
Benzoyl peroxide: a review of its current use in acne
Sagransky et al., Expert Opinion on Pharmacotherapy, 2009
Regulatory Info
Can I mix Benzoyl Peroxide with other ingredients?
Benzoyl peroxide oxidizes retinol, making it inactive. They cancel each other out. Use benzoyl peroxide in the morning and retinoid at night.
Benzoyl peroxide oxidizes vitamin C and makes it completely ineffective. Use vitamin C in the morning and benzoyl peroxide at night.
Sulfur
Both sulfur and benzoyl peroxide are strong acne fighters but together they severely dry and irritate skin.
General guidance
Benzoyl peroxide increases sun sensitivity. Make sure SPF is in your morning routine.
Both are drying. Benzoyl peroxide with AHAs can over-dry and irritate skin. If you use both, apply on alternate days.
Benzoyl peroxide and BHA both target acne but together can be very drying. Consider alternating AM and PM.
Benzoyl peroxide oxidizes vitamin C. If both are in your routine, use vitamin C in AM and benzoyl peroxide in PM.
Hydroquinone
Both can cause temporary skin staining when combined. If using together, let each fully absorb before applying the next.
Arbutin with benzoyl peroxide can cause temporary discoloration on some skin tones. Let each product fully absorb before applying the next.
Read all ingredient interaction guides for layering order and science-backed advice.