Quick Comparison
| Glycolic Acid | Hyaluronic Acid | |
|---|---|---|
| Typical Concentration | 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. | Concentrations: 0.1-2%. Higher is not always better — concentrations above 2% can feel sticky and may actually pull moisture FROM skin in dry climates. Multi-molecular weight formulations are preferred. Apply to damp skin and seal with moisturizer. |
| Application | Topical (toner, serum, peel, cleanser). Leave-on products are more effective than wash-off. Apply to dry skin at night. | Topical (serum, cream, mask). Apply to damp skin and layer occlusive on top. Injectable HA fillers are a separate medical category. |
| Research Papers | 9 papers | 10 papers |
| Categories |
Mechanism of Action
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.
Hyaluronic Acid
Hyaluronic acid is a glycosaminoglycan (GAG) composed of repeating D-glucuronic acid and N-acetyl-D-glucosamine disaccharides. Its hydroxyl and carboxyl groups create strong hydrogen bonding with water—each molecule binds up to 1000x its weight in water. High molecular weight HA (>1000 kDa) forms a viscoelastic film on the stratum corneum, reducing transepidermal water loss (TEWL). Medium weight (100-1000 kDa) penetrates the upper epidermis. Low molecular weight HA (<100 kDa) reaches the dermis and binds CD44 and RHAMM receptors on fibroblasts, triggering ERK and PI3K signaling that stimulates fibroblast proliferation, hyaluronan synthase (HAS2) expression, and collagen I/III synthesis. Sodium hyaluronate—the salt form—has improved stability and penetration. Multi-weight formulations provide surface hydration and deeper dermal stimulation.
Risks & Safety
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.
Hyaluronic Acid
Common
Stickiness at high concentrations. In very dry/arid climates, HA can draw moisture from deeper skin layers to the surface where it evaporates.
Serious
None.
Rare
Mild irritation from very low molecular weight HA penetrating too deeply.
Full Profiles
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.
Hyaluronic Acid →
The most popular hydrating ingredient in skincare. Hyaluronic acid (HA) is a glycosaminoglycan naturally produced by the body that can hold up to 1,000x its weight in water. In skincare, different molecular weights serve different functions: high molecular weight HA sits on the skin surface forming a moisture barrier, while low molecular weight HA penetrates deeper layers for plumping hydration.