Moisture Barrier In The Skin: What It Does & How To Help Care For It

The skin barrier sounds like a simple concept but is actually quite complex when you get into the details. There are a lot of parts that go into making it function properly, and each of those parts works with the others to strengthen the skin.

One such part is something called the "moisture barrier." But what exactly is that, and how does it relate to the larger skin barrier? This is where it takes a bit of nuance.

In the past, we've talked about the skin barrier as something of a "brick and mortar" visual—and while this isn't entirely inaccurate, it's not the whole picture. 

"We were taught initially that the skin barrier is this brick and mortar. The bricks are dead skin cells, and the mortar is the fat. It's almost like a wrap around the body. And just in the last couple of years, we know that it's so much more dynamic than that," says board-certified dermatologist and mbg Collective member Whitney Bowe, M.D.

The moisture barrier is an outer layer of skin that ensures your skin is hydrated by trapping and holding water. One of the ways your skin dries out is when water escapes your barrier and evaporates into the air around you—or what's called transepidermal water loss. So keeping that moisture layer strong is essential to overall skin function. 

So what makes up this moisture barrier? A combination of proteins from dead skin cells and lipids. To go back to the brick-and-mortar analogy I alluded to in the introduction, if there was a part of the skin that resembled the brick wall, it'd be this. (I told you it wasn't an entirely inaccurate visual!)

To contextualize this moisture barrier (or stratum corneum, which I'll use interchangeably from here on out now that we've established what they are), we must understand the skin barrier writ large. The barrier isn't only this brick-and-mortar part, as we once thought. "There are actually four main components to the skin barrier," says Bowe. "It also contains components such as the skin microbiome, acid mantle, and the skin's own immune system." 

All these parts work together to fortify and support each other. For example, the skin microbiome is able to help produce byproducts (called postbiotics) such as lipids and peptides to feed back into the stratum corneum. On the flip side, when one is weak, it can hinder the rest. For example, if the acid mantle is disrupted, it can change the microflora of the biome or strip the moisture barrier of lipids. 

And why is it so vital to tend to all these parts? Because a strong skin barrier literally means a better protected body. "It protects us from mechanical injury, low humidity, cold, heat, sun, wind, chemical exposure, bacteria, viruses, fungi, and other pathogens," explains board-certified dermatologist Hadley King, M.D., stating that, "a healthy barrier is critical to normal skin function."

A well-formulated hydrator will do wonders for your skin and moisture barrier. Look for options with a robust assortment of moisturizing botanicals and lipids to feed that lipid layer. There are many solid ingredients out there, so just look for those you like the texture and appeal of.

A few to keep in mind: Aloe vera is a lightweight humectant, shea butter is a rich fatty-acid-filled butter, oat oils and extracts are ideal for sensitive skin, or squalane works well with your skin's natural oils. 

Additionally, we recommend looking for options that not only treat the moisture barrier but also tend to the other areas of the skin barrier. Biotic ingredients can feed and nurture your skin's microflora, helping support the balance, calming the skin, and improving the overall health of your skin.

We can't avoid all external stressors, and we'd never recommend you try. But you can make habit tweaks to ensure you're helping your skin deal with the onslaught of free radicals that come with these stressors.

Given your moisture barrier is made up of proteins from skin cells and lipids, feeding your body a supporting supply of them can help your overall skin health. Look for collagen-containing foods, a wide variety of healthy fats, and of course skin-supporting antioxidants. All of these can support your skin barrier from the inside out.

Your moisture barrier is a critical part of the overall skin barrier function, and to care for one part means to care for all. The moisture barrier itself (also called the stratum corneum) is the layer made up of proteins and lipids that traps in water and keeps all below it protected.