Rumor has it that Cleopatra — known for her beauty and charm — took daily milk baths that contributed to her glowy, smooth skin. The science behind it actually makes sense: Dairy (as well as fruits, vegetables and some plants) naturally produces lactic acid, an exfoliant that is gentle enough for even the most sensitive skin types. Today, the idea of pouring gallons of milk into your tub is probably a bit extravagant for most, but luckily there are more efficient, effective ways to infuse lactic acid into your routine: The hero ingredient is found in many over-the-counter products to achieve similar silky-soft skin results.
If beauty hacks used by the Egyptian royal isn’t enough to convince you that you should be using a lactic acid immediately, we had the pros provide a beginner’s guide to everything you need to know so you can decide whether or not it is right for you (with the green light from your dermatologist, of course).
Q: What is lactic acid?
“Lactic acid is an alpha hydroxy acid (an AHA) that’s a natural chemical exfoliator, which helps remove the top layers of dead skin cells and increases cell turnover,” says Y. Claire Chang, M.D.,, a board-certified cosmetic dermatologist at Union Square Laser Dermatology in New York. Lactic acid can be produced synthetically (in products), through a biologic process (like when you exercise), and can be found naturally in certain foods like milk and yogurt. “It has a similar structure as glycolic acid, but it’s known to be more gentle on your skin because it has a larger molecule size that makes it less potent and more tolerable,” she adds.
Q: What are the main uses of lactic acid and what do the different strengths mean?
“Lactic acid not only stimulates the exfoliation of skin cells but also increases ceramides, an important fatty acid in your skin to serve as a protective skin barrier,” says Melissa Kanchanapoomi Levin, M.D., New York-based dermatologist and founder of Entiere Dermatology. “At higher concentrations, lactic acid is not only a gentle exfoliating option, but at lower concentrations it also increases the skin’s moisture level. It’s an amazing humectant, which means it has the ability to pull water into the outer layer of the skin,” she adds.
Q: Who might benefit the best from lactic acid?
“Lactic acid can be great for any skin type, and because lactic acid tends to be more gentle than other chemical peels, it’s an optimal option for those with sensitive skin — still using caution, of course,” says Chang. A true multitasking ingredient, it can also be used by people who are looking to treat hyperpigmentation and pigment conditions (like melasma), sun spots, enlarged pores, uneven complexion and texture, and signs of aging. “It can also treat skin conditions like keratosis pilaris — more commonly known as ‘chicken skin,’” adds Chang.
Q: Should anyone avoid it?
It is more about making sure you are layering your products properly. “If your existing routine already incorporates other AHAs, beta hydroxy acids (BHAs), or retinoids, you may encounter too much irritation, dryness, flaking or redness,” says Levin.
Q: Which products can you pair it with?
While you should always use sunscreen, now more than ever should you remember your daily dose of SPF. “The healing skin is particularly sensitive to the sun when using lactic acid in your routine,” says Chang. The exfoliating effect of AHAs can make your skin more sensitive to the sun’s ultraviolet radiation, so slather on a broad-spectrum formula with at least an SPF of 30. “You can combine it with moisturizing ingredients like ceramides and hyaluronic acid to increase your skin’s overall hydration.”
Q: How often should you use it?
This depends on the concentration of lactic acid that you use. “In general, weaker strength lactic acids can be used daily, while higher strength lactic acids should be limited to two or three times per week as tolerated. If your skin is getting too irritated, red, and dry, it is important to take a break for a few days to allow your skin to recover,” says Chang.
Q: When will I start seeing results?
That depends on the strength of lactic acid that you start with, but you will probably notice a difference in brightness right away thanks to its exfoliating properties. But for best results over time, “start with a lower percentage of five to 10 percent and then assess how your skin looks after regular use over one month. If the results are effective, I recommend sticking to the same percentage, but if you’re not experiencing enough of a difference — and your skin’s tolerating it well — you can slowly increase the strength,” says Levin.
Q: What does it feel like when you use it?
It depends on the strength and amount of lactic acid in the product. “You might feel a mild tingling or slight burning sensation while others may not feel anything at all. It’s normal to get some mild, temporary redness or irritation during and after using a lactic acid treatment,” says Chang. Stop using it if you feel excessive irritation and “if you’re experiencing extreme itchiness, swelling or pain, it could be contact dermatitis,” she adds. If that occurs, head over to your dermatologist stat to get it checked out.
Q: What is the most common mistake when using lactic acid?
“Especially if you have sensitive skin, it’s important not to skip patch testing,” says Chang. “Apply a thin layer of product to your forearm or neck to see whether or not you get a reaction.” It is important to do it for a few days in the same area, as sometimes allergic reactions can be delayed.
Q: What is the most surprising thing people find when they start using it?
“Many patients are surprised at how well-tolerated lactic acids are. Over-the-counter formulations are typically very gentle. You’ll find that with daily use, there will be a gradual, noticeable improvement in overall complexion and tone of your skin,” says Chang.