Quick Comparison
| Gluconolactone (PHA) | Urea | |
|---|---|---|
| Typical Concentration | Concentrations: 4-15%. Can often be used daily even by sensitive skin types. Apply morning or night. No sun sensitivity increase (unlike AHAs). pH range: 3.5-4.5. | Moisturizing: 2-10%. Mild exfoliation: 10-20%. Strong keratolytic: 20-40%. For face: stay at 5-10%. For body rough patches: 10-20%. For calluses/severely rough skin: 40%. Apply to damp skin and seal with cream. |
| Application | Topical (serum, toner, cream). Gentle enough for daily use on most skin types. | Topical (cream, lotion, gel). Apply to damp skin. Eucerin and CeraVe have well-known urea-containing lines. |
| Research Papers | 4 papers | 10 papers |
| Categories |
Mechanism of Action
Gluconolactone (PHA)
Gluconolactone hydrolyzes desmosomal proteins and glycosaminoglycan bonds between corneocytes in stratum corneum, promoting desquamation. Large molecular size (178 Da vs glycolic acid 76 Da) means slow, even penetration through lipid bilayer — no irritation-causing 'hot spots' of concentrated acid. Gentle, sustained exfoliation. Six hydroxyl groups per molecule make it a potent humectant, forming hydrogen bonds with water and drawing moisture into stratum corneum. Chelates iron and copper ions, reducing metal-catalyzed free radical formation. Has antioxidant properties. Unlike AHAs, does not increase UV sensitivity. Lactone ring hydrolyzes to gluconic acid at skin pH. Ideal for sensitive skin, rosacea, those intolerant of glycolic or salicylic acid.
Urea
At low concentrations (<10%), urea acts as a humectant — small molecule (60 Da) absorbing into stratum corneum, drawing water via hydrogen bonding to carbonyl and amine groups. Part of endogenous NMF (filaggrin degradation products with amino acids, lactate), highly biocompatible. Integrates into corneocyte envelope, supports aquaporin-3 water transport. At higher concentrations (>10%), denatures keratin (K1, K10) by disrupting hydrogen bonds in alpha-helical structure and disulfide bridges in cornified envelope, causing corneodesmosome degradation and desquamation. Keratolytic via direct protein denaturation, not enzymatic. Dual mechanism — humectant at low dose, keratolytic at high — versatile for hydration and hyperkeratotic conditions (psoriasis, keratosis pilaris).
Risks & Safety
Gluconolactone (PHA)
Common
Essentially none — one of the most tolerated exfoliants. Slight stickiness.
Serious
None.
Rare
Mild irritation in extremely reactive skin.
Urea
Common
Stinging on broken or irritated skin (more likely at higher concentrations).
Serious
None.
Rare
Contact dermatitis (uncommon).
Full Profiles
Gluconolactone (PHA) →
A polyhydroxy acid (PHA) — the gentlest class of chemical exfoliants. Gluconolactone has a very large molecular size, so it works extremely slowly on the skin surface without penetrating deeply. This makes it ideal for extremely sensitive skin, rosacea-prone skin, and those who cannot tolerate AHAs or BHAs. It also acts as a humectant, drawing moisture into the skin as it gently exfoliates.
Urea →
A natural component of the skin's Natural Moisturizing Factor (NMF) that serves as both a humectant and a keratolytic depending on concentration. At low concentrations (2-10%), urea hydrates by drawing water into the stratum corneum. At higher concentrations (20-40%), it breaks down keratin protein, making it a powerful treatment for rough, thickened, or keratotic skin conditions like keratosis pilaris, calluses, and psoriasis.