Here’s a little riddle for ya: What has more than 1.7 billion (yes, with a “b”) views on TikTok, plays a role in conditions ranging from acne to eczema, and is currently all the rage when it comes to skin care products? If you guessed the skin barrier—congratulations, you are correct.

Unlike some other trending skin care topics, the skin barrier is a very real thing, and one that plays an integral role in healthy skin function, according to the experts SELF spoke with. We’ll get to the specifics in a moment, but the skin barrier is well, exactly what it sounds like—a protective layer that’s responsible for keeping the good stuff in and the bad stuff out.

A variety of factors can take a toll on this skin shield of sorts—it’s why #skinbarrierrepair videos are also racking up millions and millions of views on TikTok and allegedly barrier-repairing products are all over the place. Here, top dermatologists explain exactly why you should care about the skin barrier and how to tell if yours needs a little extra TLC.

What is your skin barrier, anyway?

“In the simplest terms, it’s the skin’s protective layer,” Mona Gohara, MD, associate clinical professor of dermatology at the Yale School of Medicine, tells SELF. “Our skin is what protects our body, and the skin barrier is what protects the skin.” Technically speaking, this protective layer is called the stratum corneum, the outermost layer of the epidermis.1

To get a better sense of how the stratum corneum functions, it might be helpful to picture a brick wall: “The ‘bricks’ are cells called corneocytes, which are held together by the ‘mortar,’ a mix of lipids including fatty acids, cholesterol, and ceramides,” Robyn Gmyrek, MD, a board-certified dermatologist at Union Derm in New York City, tells SELF. This “brick wall” creates a barrier that prevents harmful bacteria, chemicals, irritants, and allergens from getting into the skin, while simultaneously locking in necessary hydration, Dr. Gmyrek explains.

What kinds of things can affect the skin barrier?

Really, the question should be what doesn’t affect it. A bunch of internal and external factors can damage or weaken the stratum corneum, according to the dermatologists we talked to. For example, some people are naturally deficient in filaggrin, a protein that strengthens the skin barrier, making them more predisposed to dryness and irritation, Dr. Gohara says.2 (More on other signs that your skin barrier isn’t in great shape in a sec.) 

Externally, many grooming and skin care routines can also change and damage it, such as using harsh soaps, over-exfoliating, taking extra-hot showers, and waxing, she adds. “Environmental factors can also weaken the skin barrier, including low humidity and dramatic temperature changes,” Naana Boakye, MD, a board-certified dermatologist and founder of Bergen Dermatology in Englewood Cliffs, New Jersey, tells SELF.3 All of the above can alter and deplete those aforementioned lipids, that “mortar” in between the cells. Essentially, that brick wall that was once solid can start to develop cracks and crevices.

Source: SELF