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Lactic Acid in skincare
Gentle AHA with built-in humectancy; ideal for sensitive skin exfoliation.
PM use preferred due to its AHA exfoliant activity causing mild photosensitization. Always use SPF 30+ in AM when using lactic acid products. At very low concentrations (<5%) in leave-on products functioning primarily as a humectant and NMF component, AM use is more tolerable than glycolic acid at equivalent concentrations. Clinical and FDA AHA guidance recommends SPF with any AHA leave-on product regardless of time of application.
What it is
Lactic Acid (2-hydroxypropanoic acid) is the second-smallest AHA and naturally occurs in the skin's Natural Moisturizing Factor (NMF). Unlike glycolic acid, it has mild humectant properties alongside exfoliant action. Also stimulates ceramide synthesis, supporting barrier function. Used at 5–10% for home use (pH 3.5–4.0); professional peels at 30–70%. Produces less stinging than glycolic acid. Effective at reducing melasma at 10% concentration.
The facts
| Category | AHA (Alpha Hydroxy Acid) |
| Typical use | Evening |
| Concentration YARAI treats as a full dose | 10% |
Why the amount matters, not just the presence
Most ingredient checkers tell you whether something is in the bottle. That is a smaller question than it sounds. Lactic Acid at 10% and lactic acid at a trace level are not the same ingredient in any way that affects your skin.
An ingredient list is ordered by quantity, so position carries real information. YARAI reads that position and scores accordingly, which is why the same ingredient can land differently in two different products.
The honest limit: a list gives order, not percentages. Estimating concentration from position is an estimate. It is a better estimate than ignoring position, and it is still an estimate. We would rather tell you that than let a number look more certain than it is.
Using it with something else
Lactic acid appears in 3 of the pairs YARAI checks. Each page gives the severity, the chemical mechanism, the evidence tier and the source:
- Can you use retinol and lactic acid together?
- Can you use niacinamide with AHA or BHA acids?
- Can you use copper peptides with vitamin C or acids?
Common questions
What does lactic acid do in a skincare product?
Gentle AHA with built-in humectancy; ideal for sensitive skin exfoliation.
How much lactic acid should a product contain?
YARAI treats 10% as a full dose for this ingredient. Below that, the ingredient is present but is scored as contributing less. An ingredient list gives you the order of ingredients, not their percentages, so this is an estimate read from position rather than a measurement.
When should I use lactic acid?
PM use preferred due to its AHA exfoliant activity causing mild photosensitization. Always use SPF 30+ in AM when using lactic acid products. At very low concentrations (<5%) in leave-on products functioning primarily as a humectant and NMF component, AM use is more tolerable than glycolic acid at equivalent concentrations. Clinical and FDA AHA guidance recommends SPF with any AHA leave-on product regardless of time of application.
Check your own products
Point your camera at a product. YARAI identifies it from the label, finds that product's full ingredient list from published sources, and scores it. No barcode and no box needed, which is how it handles imported and small-brand products.
Concern level, category and thresholds on this page are read directly from the same data the YARAI app scores with, so this page and the app cannot disagree. EU figures cite Regulation (EC) No 1223/2009. Last built 2026-10-12. Nothing here is medical advice.