What is it? Lactic acid is part of the alpha hydroxy acid (or AHA) family, which includes ingredients derived from sugar cane, fruit and milk. Specifically, lactic acid comes from milk; after it undergoes fermentation, it's a powerful exfoliating ingredient that regularly appears in skincare products.
Similar to the widely popular AHA glycolic acid, lactic acid reduces fine lines, wrinkles, age spots and hyperpigmentation while improving the skin's texture and promoting collagen production. But unlike glycolic acid, lactic acid typically doesn't cause allergic reactions or irritation.
You'll find it in: You can find lactic acid in a wide variety of skincare products today, especially because it's gentle enough for people with sensitive skin, rosacea or acne. Its ability to exfoliate puts lactic acid in many dry skin moisturizers, as it encourages the upper layer of skin cells to shed quicker, leaving the healthier cells behind. Plus it helps moisturizers prevent the skin's natural oils and water from escaping.
In addition, because lactic acid reduces the appearance of wrinkles, age spots and hyperpigmentation, it's used in many cleansers and anti-aging lotions. It's often found in acne products as well, as it's believed lactic acid reduces acne lesions if used appropriately. Alternately, too much exfoliation can cause more acne than you had to begin with, so just make sure to follow the directions on the product. To be on the safe side, start with a skincare product that contains a low concentration of AHA ingredients, only use it every other day at first and then work your way up to daily use.
Our product picks: If you're looking for deep exfoliation but concerned about irritating your skin, you might want to try Philosophy Microdelivery Peel, which contains lactic acid/salicylic acid activating gel that not only exfoliates but also replenishes skin with vitamin C.
What to expect: Although lactic acid is mild, it's possible to react adversely to it. If any burning, irritation, peeling, redness or stinging persists, make sure to contact your doctor right away. Also note that as with any AHA, lactic acid makes skin more vulnerable to UV radiation, so you'll want to use plenty of sunscreen with SPF 15 or higher.
Normally, you can expect the ingredient to smooth and replenish your skin. For example, according to a 2002 study, after 22 weeks, researchers found applying 8 percent lactic acid twice a day, compared with a placebo, significantly improved the appearance of fine wrinkles in female participants.
Who should avoid it: As long as it's used properly, lactic acid is appropriate for all skin types, but those with extremely sensitive skin should be cautious of higher-strength lactic acid products, just like they should be wary of all concentrated skincare products. You'll also want to avoid these higher-strength products if you're using retinol.
Women who plan to become pregnant, are pregnant or nursing should discuss the benefits and risks of using lactic acid with their doctor, because it's unclear whether lactic acid is passed on through breast milk.
See also:
Idebenol and Idebenone
10 Steps to a Perfect Shave
Indoor Tanning: Safety Facts
6 Ways to Care for Skin in College
Ways to Drive Out Dry Skin