Quick Comparison
| Azelaic Acid | Sulfur | |
|---|---|---|
| Typical Concentration | OTC: 10% (The Ordinary). Prescription: 15% gel (Finacea for rosacea), 20% cream (Azelex for acne). Apply twice daily. Well-tolerated but may sting/itch initially. Full effects at 8-12 weeks. | Concentrations: 2-10% in OTC products. Leave-on treatments: 3-8%. Wash-off: 5-10%. Can be used daily for mild acne. Sulfur masks (De La Cruz sulfur ointment) applied for 10-20 minutes are popular. Drying — follow with moisturizer. |
| Application | Topical (gel, cream, serum). Slightly gritty texture in some formulations. Apply to clean skin. | Topical (ointment, mask, cleanser, spot treatment). Leave-on or wash-off. Apply to clean skin. |
| Research Papers | 9 papers | 10 papers |
| Categories |
Mechanism of Action
Azelaic Acid
Azelaic acid exhibits multi-modal activity: (1) Tyrosinase inhibition—competitively inhibits tyrosinase selectively in hyperactive melanocytes (melasma, PIH) while sparing normal ones; may involve mitochondrial enzyme interference in dysregulated melanocytes. (2) Antimicrobial—bacteriostatic against Cutibacterium acnes by inhibiting bacterial protein synthesis. (3) Comedolytic—normalizes follicular keratinization, reducing hyperkeratinization and corneocyte cohesion; may modulate keratinocyte differentiation. (4) Anti-inflammatory—scavenges ROS, inhibits neutrophil free radicals, reduces pro-inflammatory cytokines. Inhibits 5-alpha-reductase in sebocytes, potentially reducing sebum. Multi-pathway activity explains efficacy in acne, rosacea, and hyperpigmentation. Safe during pregnancy.
Sulfur
Elemental sulfur (S8) reacts with cysteine residues in stratum corneum proteins to form hydrogen sulfide (H2S) and thiol derivatives, reducing disulfide bonds in keratin K1/K10 and cornified envelope — loosening corneocyte cohesion and promoting desquamation. Breaks hyperkeratotic plug in follicular ostia, unclogging pores. Bacteriostatic against Cutibacterium acnes through metabolism and membrane disruption. Reduces sebum production, possibly via anti-androgenic effects on sebaceous glands. Antifungal against Malassezia furfur (seborrheic dermatitis, pityrosporum folliculitis) via ergosterol synthesis inhibition. Anti-inflammatory effects may involve H2S signaling — endogenous H2S has vasodilatory properties. Mild comedolytic. Well-tolerated: works primarily on stratum corneum without deep penetration.
Risks & Safety
Azelaic Acid
Common
Stinging, burning, itching on initial application (usually subsides within 2 weeks). Mild dryness.
Serious
None. Safe during pregnancy and breastfeeding.
Rare
Allergic contact dermatitis, hypopigmentation (rare at cosmetic concentrations).
Sulfur
Common
Drying, distinctive rotten-egg smell, may bleach fabrics.
Serious
None at cosmetic concentrations.
Rare
Allergic reaction (sulfur allergy is distinct from sulfonamide or sulfite allergy).
Full Profiles
Azelaic Acid →
A dicarboxylic acid naturally produced by yeast on the skin. Azelaic acid is a true multi-tasker that treats acne, rosacea, and hyperpigmentation simultaneously. It is one of the few active ingredients considered safe during pregnancy, and it uniquely targets only abnormal melanocytes — meaning it brightens dark spots without lightening normal skin. Effective for both inflammatory acne and post-inflammatory hyperpigmentation (PIH).
Sulfur →
One of the oldest acne treatments, used for centuries. Sulfur has keratolytic (exfoliating), antimicrobial, and anti-inflammatory properties that make it effective for acne, seborrheic dermatitis, and rosacea. It has a distinctive smell but is gentler than benzoyl peroxide and works well for people who cannot tolerate BP or salicylic acid. Often found in traditional 'sulfur soap' and spot treatments.