What Glycolic Acid Does in Dermatological Treatments
Glycolic acid functions as a chemical exfoliant that removes dead skin cells, stimulates keratinocyte proliferation, and treats multiple skin conditions including acne, photoaging, and hyperpigmentation through both epidermal and dermal mechanisms. 1, 2
Primary Mechanisms of Action
Glycolic acid works through several distinct pathways:
Chemical exfoliation: As the smallest alpha-hydroxy acid (AHA), it penetrates the stratum corneum to break down intercellular bonds, facilitating removal of dead skin cells and promoting epidermal turnover 3, 4
Keratinocyte proliferation: At the molecular level, glycolic acid activates TRPV1 (acid-sensitive ion channels) in basal keratinocytes, triggering ATP release and subsequent cell proliferation in a pH-dependent manner 5
Antibacterial effects: Glycolic acid exhibits pH-dependent antibacterial activity against Cutibacterium acnes (the bacteria implicated in acne), with the nonionic form disrupting bacterial cell membranes—concentrations as low as 0.2% at pH 3.5 can kill acne bacteria 6
Dermal remodeling: Higher concentration peels (30-70%) affect papillary dermis connective tissue proteins, promoting collagen remodeling similar to TCA peels 3
Clinical Applications by Concentration
The American Academy of Dermatology stratifies glycolic acid use by concentration and treatment depth 2:
Home-use formulations (5-15%):
- Daily maintenance exfoliation for acne-prone skin, fine lines, and uneven texture 7
- Should be applied in the morning with broad-spectrum sunscreen 8
- Well-tolerated for conditions like facial plane warts 1, 7
Professional peels (30-70%):
- Very superficial peels: 30-50% applied for 1-2 minutes 2
- Superficial peels: 50-70% applied for 2-5 minutes 2
- Medium-depth peels: 70% applied for 3-15 minutes 2
- Applied every 15 days for 4-6 months for optimal results 2
Specific Conditions Treated
The American Academy of Dermatology recognizes glycolic acid for 1:
- Acne vulgaris: Both as topical agent and chemical peel, reducing inflammatory and comedonal lesions 1
- Photoaging: Removes actinic keratoses, fine wrinkles, and lentigines 4
- Hyperpigmentation: Treats melasma and post-inflammatory hyperpigmentation 3, 4
- Acne scars: Improves skin texture through dermal remodeling 1
Critical Safety Considerations
Absolute contraindications per the American Academy of Dermatology 2:
- Isotretinoin therapy within the last 6 months
- Active infection or open wounds
- Poor general health and nutritional status
Relative contraindications 2:
- Active rosacea, seborrheic dermatitis, atopic dermatitis, or retinoid dermatitis
- Recent medium-depth or deep resurfacing within 3-12 months
- History of abnormal scar formation
Primary adverse effects to monitor 2:
- Post-inflammatory hyperpigmentation (most common)
- Erosive blisters with potential scarring
- Increased photosensitivity requiring daily SPF use 8
Combination Therapy Optimization
Glycolic acid enhances outcomes when combined with other modalities 9:
- With tretinoin: Apply glycolic acid 7% in the morning and tretinoin in the evening to optimize tolerance; use gentle, non-medicated cleanser between applications 8
- With nonablative lasers/IPL: Smooths stratum corneum to reduce light scattering, enhancing laser penetration 9
- With TCA peels: Enables use of lower TCA concentrations while maintaining efficacy 9
Common Pitfall to Avoid
Do not confuse clinical peel concentrations (30-70%) with home-use formulations (5-15%)—these serve entirely different purposes and require different application protocols 2. Clinical peels require professional application, appropriate neutralization, and monitoring for complications, while home-use products are designed for daily maintenance with minimal supervision 2, 7.