Quick Comparison
| Azelaic Acid | Glycolic Acid | |
|---|---|---|
| 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. | Daily use: 5-10% at pH 3-4. Weekly peel: 10-30%. Professional peel: 30-70%. Start with 5% every other night. Increase concentration/frequency gradually. Always use SPF — AHAs increase sun sensitivity by up to 50%. Buffered formulations are gentler than free acid. |
| Application | Topical (gel, cream, serum). Slightly gritty texture in some formulations. Apply to clean skin. | Topical (toner, serum, peel, cleanser). Leave-on products are more effective than wash-off. Apply to dry skin at night. |
| Research Papers | 9 papers | 9 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.
Glycolic Acid
Glycolic acid disrupts ionic bonds between corneocytes (dead skin cells) in the stratum corneum by chelating calcium ions and lowering the calcium concentration at desmosomal junctions. This weakens corneodesmosome integrity and activates endogenous proteases (kallikrein 5 and 7), accelerating desquamation. At higher concentrations, glycolic acid penetrates the viable epidermis and dermis, where it stimulates keratinocyte differentiation and upregulates transforming growth factor-beta (TGF-β) signaling in fibroblasts. This promotes glycosaminoglycan (GAG) synthesis, type I and III collagen production via procollagen gene expression, and elastin remodeling. Its small molecular size (76 Da) and high water solubility give it the deepest penetration of any AHA. The exfoliation also improves barrier function over time by promoting proper corneocyte maturation and reducing stratum corneum compaction.
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).
Glycolic Acid
Common
Stinging, redness, peeling, sun sensitivity. Over-exfoliation damages the skin barrier.
Serious
Chemical burns from professional-strength peels without proper protocol.
Rare
Scarring from improper high-concentration use.
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).
Glycolic Acid →
The smallest and most penetrating alpha-hydroxy acid (AHA). Derived from sugarcane, glycolic acid exfoliates by dissolving the bonds between dead skin cells on the surface, revealing smoother, brighter skin underneath. It is the most studied AHA with robust evidence for improving texture, fine lines, hyperpigmentation, and overall skin radiance. The gold standard chemical exfoliant.