What Is Lactic Acid? 4 Benefits That Make This A Skin Care Fave

When it comes to skin care, most of us have a favorite acid we reach for to tackle our greatest complexion concerns. But if you have sensitive skin, you likely know that slathering any ol' acid over your complexion just isn't a good idea. So if your skin is easily irritated, the best sensitive-skin-friendly acid out there is lactic acid. It can help improve fine lines, reduce breakouts, and exfoliate dead skin. Here, our deep dive. 

Lactic acid is an alpha-hydroxyl acid (AHA), better known as an exfoliating acid that sloughs off dead skin cells (not all acids exfoliate; looking at you, hyaluronic acid). The acid is actually derived from milk (however, you can find vegan options) and is found in professional peels or infused in over-the-counter skin care products including serums, cleansers, creams, and treatments. According to board-certified dermatologist Ellen Marmur, M.D., it is generally used to exfoliate the skin, lighten dark spots, and improve the look of fine lines and wrinkles. 

When it comes to AHAs, lactic acid has one of the larger molecules in the group, which means it can't penetrate as deeply as others. This means all of the hard work of the acid happens on the surface of the skin, which decreases the amount of irritation and helps to protect the skin barrier. So, no matter whether you have sensitive skin or not, if you've found that other AHAs cause irritation, try swapping for the gentler lactic acid with the same benefits. 

Let's dive into why it's a great addition to your skin care routine. As far as peer-reviewed research goes, there's plenty of evidence to show it's safe and effective—however, it's not as widely studied as some of its other skin care counterparts like glycolic or salicylic acid. That being said, it's overwhelmingly praised by skin care experts.

Lactic acid is no newbie in the skin care world. It dates back to the days of Cleopatra. It was said that the Egyptian queen herself would bathe in milk to keep her skin looking its best. Not only was her eyeliner on point, but apparently her skin was, too. Thankfully, we don't have to soak our face in milk to get its anti-aging benefits. 

"Lactic acid is formed by a fermentation process of using bacteria to convert sugars like glucose in lactic acid," Marmur says. "It can be a white powder or a clear liquid and can be formulated with compatible ingredients in serums, creams, cleansers, and chemical peels." And although it is naturally found in dairy products including milk and yogurt, most of the lactic acid we find in topical skin care products is synthetically produced. 

As with all acids, you should always use caution (and wisdom) when adding them to your skin care routine. Marmur suggests those who are allergic or lactose intolerant should avoid lactic acid unless it's under the guidance of their dermatologist. And even though it's a gentler option when it comes to AHAs, it's still very powerful. So, do not apply it to your skin if it's irritated or inflamed. 

Another issue: AHAs make your skin more sun-sensitive. "There are certain things you use in your routine that make your skin more photosensitive, meaning your skin burns easier, and those include AHAs," says board-certified dermatologist Whitney Bowe, M.D. Marmur also warns that some people find lactic acid makes their skin more sensitive to the sun2, so applying SPF is super important. "Make sure to be extra careful with the sun and use mineral SPF 30 or higher."  

Generally speaking, lactic acid is a great option for those newer to acids or those with sensitive skin. It's gentler than other AHAs and is chock-full of anti-aging benefits. It sloughs off dead skin, decreases hyperpigmentation, balances out moisture levels, and stimulates collagen renewal. And as with all skin care, it's always a good idea to consult with your dermatologist before using.