Lactic Acid is an alpha hydroxy acid (AHA) — a water-soluble exfoliant and humectant that gently dissolves the bonds between dead skin cells while drawing moisture into the skin. With a molecular weight of 90.08 Da (larger than glycolic acid's 76.03 Da), it penetrates more slowly and is considered among the gentlest commonly used AHAs. Naturally found in sour milk and produced during human metabolism. Registered as EU CosIng #34809. CIR classifies it as "Safe with Qualifications." SCCNFP precautionary guidance: ≤2.5% at pH ≥5.0 (not a regulatory limit — products at 5–10% are widely available). Unlike salicylic acid, lactic acid DOES increase UV sensitivity — sunscreen is essential. Found in 12,409 products.
Lactic Acid (INCI: LACTIC ACID, CAS 50-21-5) is an alpha hydroxy acid (AHA) — a water-soluble organic acid with both exfoliating and humectant properties. It is the second most commonly used AHA in skincare after glycolic acid, but is generally considered milder due to its larger molecular weight (90.08 Da vs 76.03 Da for glycolic acid). Its dual function as both an exfoliant and a humectant means it removes dead skin cells while simultaneously attracting moisture — making it particularly well-suited for dry and sensitive skin types. Lactic acid is registered in the EU CosIng database (#34809) with functions as a skin conditioning agent, exfoliant, humectant, and pH adjuster.
Lactic acid occurs naturally in sour milk and dairy products — Cleopatra's legendary milk baths were an early (if inadvertent) use of lactic acid as a cosmetic exfoliant. It is also produced naturally in the human body during anaerobic metabolism. Commercial lactic acid for cosmetics is typically produced via bacterial fermentation of corn starch or beet sugar. The CIR Expert Panel classifies it as "Safe with Qualifications" — safe at up to 10% concentration at pH ≥3.5 for consumer cosmetics, and up to 30% at pH ≥3.0 for salon/professional use, with directions for daily sun protection. Our database identifies lactic acid in 12,409 products, making it one of the most widely used AHA ingredients in skincare.
The SCCNFP (predecessor to SCCS) evaluated AHAs including lactic acid in two position papers (SCCNFP/0370/00, 2000; SCCNFP/0799/04, 2004) and established a precautionary guidance of ≤2.5% lactic acid at pH ≥5.0 for consumer cosmetic products — more conservative than the CIR limits but advisory rather than a binding EU regulatory limit (products at 5–10% are widely sold and legal in the EU). Key findings: lactic acid at 8% and pH 4.3 was milder than glycolic acid formulations at the same pH; pH is a more important factor than concentration for AHA irritancy; AHA application increases UV sensitivity (increased sunburn cell production, decreased minimal erythema dose); and 17 RIPT studies from the CIR review showed no significant sensitisation. Lactic acid carries 3 GHS hazard codes for the raw material (H314, H315, H318) — these relate to corrosion and irritation at full concentration and do not apply to cosmetic formulations at typical concentrations.
Lactic acid dissolves the intercellular bonds holding dead skin cells to the surface, promoting gentle cell turnover without the harshness of physical scrubs. Its larger molecular size (90.08 Da) contributes to slower penetration than glycolic acid, making it one of the milder commonly used AHAs. Regular use reveals smoother, brighter, more even-toned skin. SCCNFP data confirms lactic acid at 8% pH 4.3 was milder than glycolic acid formulations at the same pH.
Unlike most exfoliants, lactic acid is also a humectant — it draws water molecules into the skin and supports the natural moisturising factor (NMF). This dual exfoliant-humectant action makes it uniquely suited for dry, dehydrated, and sensitive skin types. While glycolic acid and salicylic acid can be drying, lactic acid actually supports skin hydration during the exfoliation process.
Lactic acid helps reduce dark spots, post-inflammatory hyperpigmentation (PIH), and uneven skin tone by accelerating the turnover of pigmented surface cells. Studies suggest it may also inhibit melanin production via tyrosinase inhibition. It is a popular ingredient in brightening serums and treatments for melasma and sun damage.
By promoting consistent cell turnover, lactic acid smooths rough texture, reduces the appearance of fine lines, and supports collagen production in the deeper skin layers. The SCCNFP confirmed that AHAs do not cause lasting skin barrier damage when used appropriately (long-term TEWL studies normal), though short-term barrier disruption during active exfoliation is expected. AHAs do not significantly increase percutaneous penetration of other compounds — meaning the skin's long-term structural integrity is maintained.
Suitable for: Dry, sensitive, normal, combination, and mature skin. Particularly well-suited for those who find glycolic acid too irritating. Use with caution on very reactive skin, rosacea, or active eczema. Always introduce gradually and use sunscreen daily — lactic acid increases UV sensitivity.
Lactic Acid carries a SkinSenseDiary safety rating of 3/10 — low risk. The CIR Expert Panel concluded it is "Safe with Qualifications" — safe at up to 10% concentration at pH ≥3.5 for consumer products, with sunscreen directions. The SCCNFP set more conservative precautionary guidance of ≤2.5% at pH ≥5.0 — advisory, not a binding EU limit (5–10% products are widely available). Lactic acid is among the gentlest commonly used AHAs — milder than glycolic acid at equivalent concentrations and pH. It carries only 3 GHS hazard codes (all relating to corrosion/irritation of the raw material), with no reproductive, systemic, or organ toxicity flags. 17 RIPT studies showed no significant sensitisation. Key caution: AHAs increase UV sensitivity — daily sunscreen is essential.
Increases UV sensitivity — sunscreen is essential: Unlike salicylic acid (BHA), lactic acid and other AHAs DO increase skin sensitivity to UV radiation. The SCCNFP confirmed increased sunburn cell (SBC) production and decreased minimal erythema dose (MED) after AHA use, particularly at higher concentrations (10%+ at low pH). Daily broad-spectrum SPF 30+ sunscreen is essential when using lactic acid. Evening application is strongly recommended to minimise UV exposure during peak activity. The SCCNFP advises consumer-facing UV warnings on all AHA products.
pH matters more than concentration: The SCCNFP found that pH is the most important factor affecting AHA irritancy — more important than concentration itself. A lower-pH product at 5% lactic acid may be more irritating than a higher-pH product at 10%. When choosing products, consider the pH alongside the concentration. Well-formulated products at pH 3.5–4.5 with 5–10% lactic acid offer the best balance of efficacy and tolerability.
Milder than glycolic acid: SCCNFP data confirms lactic acid at 8% pH 4.3 was milder than glycolic acid formulations at equivalent pH. This is partly attributed to its larger molecular weight (90.08 vs 76.03 Da), which contributes to slower skin penetration (pH and vehicle also play a role). This makes lactic acid a popular choice among AHAs for sensitive skin and AHA beginners.
GHS hazard codes relate to the raw material only: The 3 GHS codes (H314, H315, H318) all relate to corrosion and irritation of concentrated lactic acid. Unlike salicylic acid, lactic acid has NO reproductive toxicity, NO systemic organ toxicity, and NO sensitisation hazard codes. The safety profile of the raw material is substantially cleaner than many other active ingredients.
Lactic acid carries no substance-level reproductive or developmental toxicity classification under CLP/GHS — a significant safety advantage over salicylic acid (which carries H361d: suspected of damaging the unborn child). Lactic acid is a naturally occurring metabolite in the human body, produced during normal anaerobic metabolism and present in breast milk. At cosmetic concentrations (2–10%), systemic absorption through the skin is limited and the absorbed lactic acid is rapidly metabolised via normal metabolic pathways (converted to pyruvate, then enters the citric acid cycle). Most dermatologists consider topical lactic acid at low concentrations (≤5%) to be among the safer chemical exfoliants during pregnancy, though pregnancy-specific clinical data is limited. Avoid high concentrations (>10%) and extensive body application during pregnancy as a precaution. Lactic acid is frequently recommended as a pregnancy-safe alternative to salicylic acid and retinol for gentle exfoliation and brightening. Nursing: no specific concerns at cosmetic concentrations, though caution is always advised. Consult your healthcare provider for individual advice.
Start with a gentle, pH-balanced cleanser. Avoid using a physical scrub or exfoliating brush — combining physical and chemical exfoliation significantly increases irritation risk. Pat skin dry before applying lactic acid.
Apply your lactic acid product (toner, serum, or peel pad) to clean, dry skin in the evening. Because lactic acid increases UV sensitivity (unlike salicylic acid), evening use is strongly recommended to minimise UV exposure during peak activity. Start with 2–3 times per week and increase frequency as tolerance builds over 2–4 weeks. Avoid the eye area, lips, and any broken or irritated skin.
Allow the lactic acid to absorb for 5–10 minutes before layering other products. Follow with a hydrating moisturiser containing ceramides, hyaluronic acid, or squalane. Lactic acid's humectant properties support hydration, but a moisturiser helps seal in moisture and support barrier recovery — especially important for dry or sensitive skin types.
Apply broad-spectrum SPF 30+ every morning — this is non-negotiable when using lactic acid or any AHA. The SCCNFP confirmed that AHAs increase UV sensitivity (increased sunburn cell production, decreased minimal erythema dose). This risk is higher at concentrations above 10% at low pH. Sunscreen protects against accelerated UV damage during the exfoliation period. Reapply every 2 hours during prolonged sun exposure.
Leave-on format, typically 5–10% lactic acid. Applied after cleansing in the evening; absorbs quickly. Most popular format for targeted exfoliation and brightening. Use 2–4 times per week.
Pre-soaked pads or wash-off masks, typically 10–15% lactic acid. Applied for 5–10 minutes, then rinsed or left on. Stronger treatment option for weekly use. Good for texture and pigmentation concerns.
Lighter leave-on format, typically 2–5% lactic acid. Applied with a cotton pad or patted on after cleansing. Gentlest option; suitable for daily use once tolerance is established. Ideal for AHA beginners and sensitive skin.
Excellent combination for hydration and barrier support. Lactic acid's humectant properties complement hyaluronic acid's moisture-binding ability. Ceramides strengthen the barrier after exfoliation. Apply lactic acid first, then layer hyaluronic acid and ceramide-rich moisturiser.
A well-tolerated pairing that strengthens the skin barrier, reduces post-inflammatory hyperpigmentation, and regulates sebum. Niacinamide buffers potential irritation from lactic acid. Can be used in the same routine — niacinamide after lactic acid has absorbed.
Broad-spectrum SPF 30+ every morning is essential — not optional — when using lactic acid. AHAs increase UV sensitivity (SCCNFP confirmed). This is the most important pairing for AHA users. Zinc oxide or titanium dioxide-based sunscreens are well-tolerated by sensitive skin.
Conflict severity: HIGH (3/10). Both increase cell turnover and can cause irritation. Using them in the same routine risks over-exfoliation, redness, and barrier damage. Recommended: alternate evenings (Mon/Wed lactic acid, Tue/Thu retinol). Lactic acid + retinol is generally better tolerated than glycolic acid + retinol due to lactic acid's milder profile, but beginners should still avoid simultaneous use.
Both work at low pH and can be individually irritating. Layering simultaneously may cause excessive stinging. Consider vitamin C in the morning (with sunscreen) and lactic acid in the evening — this actually creates an ideal AM/PM routine. Experienced users with tolerant skin may layer them, but allow lactic acid to absorb fully first.
Combining lactic acid with glycolic acid, salicylic acid, or benzoyl peroxide multiplies exfoliation and irritation risk. Never use two chemical exfoliants in the same routine unless specifically formulated together. If rotating, space by 24+ hours (e.g., lactic acid Monday, salicylic acid Wednesday). Over-exfoliation is one of the most common skincare mistakes.
Found in 12,409 products in our database. Here are some well-known lactic acid options. Note: formulations change — always check the current INCI list on the product packaging or label.
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