Acid Mantle: What It Is, What It Does, Care Tips & More 

It may have a name fit for a '90s garage rock band, but don't let that radness fool you: Your acid mantle is actually one of the most crucial parts of your skin barrier. The term dates all the way back to the 1920s, when a group of researchers discovered the acidic film that rests on top of the skin's surface. Since its discovery, it's been a name typically used only by science-minded skin care experts and researchers—it never really broke into the beauty lexicon. Well, that's until fairly recently. 

As our collective understanding of skin care becomes increasingly advanced, even amateur beauty fans have started looking into the invisible shield, how it affects skin health, and what our modern skin care routines are doing to it (hint: it's not so great). 

Well, without further delay, here's what you need to know about the acid mantle. 

The acid mantle1 is the film of acidity that rests on top of the skin's epidermis and is an important player in our skin barrier function. If hearing that you have a film that covers your entire body makes you think, Huh? Where? or I don't feel it... Well, the acid mantle is actually nothing more than a mixture of your natural sebum (oil) and sweat. So the short answer is that you already know it's there; you just may not know that it has a name and a very important function in skin and bodily health. 

Considering the point of the acid mantle is to be slightly acidic, pH of course plays a big role. So let's go over pH for a moment so you're well acquainted with the concept. (You can also venture over to our full explainer if you want more information.) The pH range of the skin on your face and body fluctuates between 4.7 and 5.752. For context, the pH scale ranges from 0 to 14; 7 is considered neutral (water has a pH of 7); anything below it is acidic, and anything above is alkaline. Keeping your skin's pH within this range—without too dramatic fluctuations or too frequent changes—will help keep the acid mantle intact. 

The reason we care so much about this layer is that it has some fairly important functions: 

We often say that the skin is your body's first line of defense; well, the acid mantle is the skin's first line of defense. Acidity "helps inhibit the growth of pathogens," notes physician Kara Fitzgerald, N.D., who explains that opportunistic bacteria tend to do better in alkaline environments.  

Board-certified dermatologist Mamina Turegano, M.D., agrees: "That slightly acidic state serves almost like a protective shield to various invaders like unwanted bacteria or other microbes and contaminants."

That being said, remember: You still want bacteria and microorganisms on the skin. Together, these are collectively called the skin microbiome, and when it's balanced, it helps temper inflammation, improves our immune function, and fights environmental aggressors. So when your acid mantle is intact, the good bacteria are allowed to do their jobs better.

The acid mantle also has a role to play in our skin barrier function. When your barrier is compromised, your skin isn't able to inhibit transepidermal moisture loss (i.e., the evaporation of water through the skin). And while there are other components of your skin barrier function—ceramides, the microbiome, collagen, and the like—keeping a strong acid mantle will certainly help overall. 

As the skin's first line of defense, the acid mantle comes into contact with quite a bit of potentially harmful aggressors—as well as some natural changes that are somewhat out of our control: 

Tending to your mantle is actually not that hard: The most important lesson we can impart to you is to simply be gentle and kind. Since your acid mantle happens naturally, you don't need to do anything proactive to encourage its formation.

Instead, just be mindful of the cleansers you are using: Make sure they are not too stripping (hint: your skin should never feel "tight" after washing; just clean, hydrated, and refreshed). You can also reevaluate how often you wash your face. Perhaps just as damaging as a harsh face or body wash is the act of washing more than you need. A good rule of thumb is to always wash your face before bed, but the rest is up to your skin's needs. As for the body, here are our guidelines for showering frequency.

You can also use hydrators to your advantage by using products formulated with barrier-supporting, biome-friendly, and pH-balancing ingredients. Look for things like ceramides, plant oils, antioxidants, shea butter, as well as pre-, pro-, and postbiotics. This is especially helpful for body parts that you have to wash with more frequency, and thus may have a more vulnerable acid mantle—oh, yes, we're talking about hands. Since hand washing is a needed part of daily hygiene, protecting the mantle in this area really comes down to selecting a hydrating wash and applying a hand cream immediately following.

You may not know its name, but the acid mantle is a natural part of your skin's surface—and performs some very important functions, primarily barrier protection. The good news is that taking care of it is pretty easy: Just be kind, and less is always more.