Quick Comparison
| Benzoyl Peroxide | Salicylic Acid | |
|---|---|---|
| Typical Concentration | Concentrations: 2.5%, 5%, 10%. 2.5% is as effective as 10% for most people with significantly less irritation. Apply as a thin layer to acne-prone areas. Short-contact therapy (apply for 5-10 minutes then rinse) reduces irritation while maintaining efficacy. Bleaches fabrics — use white towels and pillowcases. | Concentrations: 0.5-2% for daily use products (cleansers, toners, serums). Up to 30% for professional peels. Start with 0.5-1% every other day and increase. Leave-on products are more effective than wash-off. For body acne (back, chest): 2% is standard. |
| Application | Topical (wash, gel, cream, spot treatment). Short-contact therapy: apply 2.5% for 5-10 minutes, then rinse — reduces irritation while maintaining antibacterial activity. | Topical (cleanser, toner, serum, spot treatment, body wash, peel). Leave-on products provide better efficacy than wash-off. |
| Research Papers | 9 papers | 10 papers |
| Categories |
Mechanism of Action
Benzoyl Peroxide
Benzoyl peroxide decomposes on skin, generating benzoic acid and reactive oxygen species (peroxyl and hydroxyl radicals). Cutibacterium acnes is an obligate anaerobe thriving in oxygen-depleted follicles; BPO-derived oxygen creates an aerobic environment while free radicals cause non-specific oxidative damage to bacterial membranes, proteins, and DNA. Because this does not target a specific bacterial pathway (unlike antibiotics), C. acnes cannot develop resistance—BPO remains effective indefinitely. Mild comedolytic activity through oxidative effects on follicular keratin. Anti-inflammatory effects from neutrophil modulation. 2.5% achieves similar bacterial kill to 10% with less irritation.
Salicylic Acid
Salicylic acid (ortho-hydroxybenzoic acid) is a lipophilic beta-hydroxy acid—the ortho hydroxyl enables sebum and follicular lipid solubility, unlike water-soluble AHAs. It penetrates the pilosebaceous unit and induces desmolysis: disruption of desmosomal attachments and corneodesmosomes, accelerating desquamation of pore-clogging debris. Inside the follicle, it dissolves sebum and keratin plugs (comedolysis). Salicylic acid inhibits COX-1 and COX-2, reducing prostaglandin synthesis—the same anti-inflammatory mechanism as aspirin—decreasing erythema and swelling. Bacteriostatic against Cutibacterium acnes through membrane disruption and pH reduction. May reduce sebum production. Small size (138 Da) and lipophilicity enable follicular penetration to depths AHAs cannot reach.
Risks & Safety
Benzoyl Peroxide
Common
Dryness, peeling, redness, bleaching of hair, towels, and clothing.
Serious
Allergic contact dermatitis (uncommon but can be severe — patch test first).
Rare
Severe allergic reaction with swelling.
Salicylic Acid
Common
Dryness, peeling, mild stinging. Over-use can compromise the skin barrier.
Serious
Salicylate sensitivity (rare) — avoid if allergic to aspirin. Not recommended in pregnancy at high concentrations.
Rare
Severe peeling from over-application.
Full Profiles
Benzoyl Peroxide →
The most effective OTC acne treatment and one of the few topical treatments that kills acne-causing bacteria (C. acnes) without promoting antibiotic resistance. Benzoyl peroxide works through oxidation — it releases oxygen into pores, creating an environment where anaerobic bacteria cannot survive. It is one of three first-line acne treatments (alongside adapalene and salicylic acid) recommended by dermatological guidelines.
Salicylic Acid →
The only beta-hydroxy acid (BHA) used in skincare. Salicylic acid is oil-soluble, meaning it can penetrate into pores and dissolve the sebum and dead skin that cause blackheads and acne. This makes it fundamentally different from AHAs (which only work on the skin surface). It also has direct anti-inflammatory properties, reducing the redness and swelling of acne lesions.