Lactic Acid

What it is

Lactic acid is an alpha hydroxy acid, or AHA, found in exfoliating skincare. It can be produced by fermentation for cosmetic use and is used in toners, serums, masks and moisturizers. Compared with glycolic acid, lactic acid has a larger molecular size, so it is often described as a gentler AHA. That is a general comparison, not a guarantee: the finished formula, its strength and how often you use it all count.

Lactic acid also functions as a humectant, helping attract water to the skin’s outer layers. It is different from salicylic acid, which is a BHA. For all exfoliating products, directions are more useful than guessing from a concentration or ingredient name.

What it does

• Exfoliates the surface. It helps loosen dead skin cells and can make rough texture look smoother.
• Helps skin look brighter. Consistent use may soften the look of dullness and uneven tone over time.
• Supports hydration. As a humectant, lactic acid can help the outer layers of skin hold water.
• May cause irritation. Stinging, dryness, redness or flaking can occur, especially if you use it too often or combine it with other actives.

Who it suits

Lactic acid may suit someone who wants an AHA for the look of dullness or rough texture and prefers a formula that also offers humectant properties. A product described as gentle can still bother sensitive or compromised skin, so start slowly and avoid applying it to irritated areas. If exfoliation does not agree with your skin, you do not need to push through. Ask a dermatologist about persistent or painful skin concerns.

What to pair it with, and what not to

Use lactic acid with a basic cleanser and moisturizer, and apply sunscreen as directed during the day while using exfoliating acids. A hydrating product with hyaluronic acid can fit in the same routine if it feels comfortable. There is no need to add multiple acid products to get a useful routine.

Avoid over-layering it with glycolic acid, mandelic acid or salicylic acid. Be similarly cautious with retinoids, since several active steps can make irritation harder to pin down. Add one product at a time, patch-test first and take a break if redness or stinging sticks around.

Skin Realist check: Gentle is not a lifetime membership card. Even a mild-sounding product gets to be evaluated by the face wearing it.