Building a better skin barrier

Is your face a glazed doughnut or a dewy dumpling? I don’t mean which of these foods are stuck on your face. Instead, these are all recent skin care trends, which, despite some key differences, share a similarity beyond their gastronomically delightful nomenclature: the popular belief that skin should glow. It should be radiant, lustrous, luminous — and even, as the aptly named glass skin trend implies, almost translucent.

In the effort to go for glass, however, it’s important to remember what skin really is: a barrier. “It’s not there just to hold everything in place,” says cosmetic chemist Valerie George, who is the CEO of Simply Beauty Group in Dallas. “It’s actually the first line of defense from pathogens entering our body.” Skin keeps out not only germs and allergens, but also other external substances. That includes water — so we can swim without turning into sponges — and skin care ingredients that would irritate if too much were absorbed.

Not too long ago, George says, it was popular to rigorously exfoliate with abrasive scrubs and acids to slough off the dead cells in the skin’s top layers. “It kind of wrecked people’s skin,” she says. “So now we’re really focused on putting the barrier back.” Now, influenced by the popularity of Korean regimens, Western trends have shifted to focus on restoring the barrier, which leads to clear, smooth, healthy looking skin.

The first step? Hydration. Skin “can’t provide that barrier function as well if it’s all dried out,” says cosmetic dermatologist Hadley King of Weill Cornell Medicine in New York City. (Picture your dry, cracked hands in the winter. Those cracks allow bacteria and irritants to get in.) Skin is always losing water, which is why moisturizing is helpful. Many moisturizers contain humectants such as glycerin and hyaluronic acid, which bind well with water and attract moisture from both the atmosphere and the skin’s deeper layers. But that water can easily evaporate. That’s where common occlusive ingredients, such as waxes and oils, come into play. They sit on top of the skin and physically block water loss. Hydration is key to glowy skin trends that promote a “wet” look, with a moistness that can be achieved by slathering on ingredients called emollients, which reflect light.

Healthy skin also benefits from active ingredients that target skin cells’ metabolic processes — things like retinoids, vitamin A–based compounds that tackle wrinkles, or niacinamide, a type of vitamin B with antioxidant benefits. Unlike humectants and occlusives, which interact with dead cells in the stratum corneum, the skin’s top layers, active ingredients need to do their work in living cells. Reaching those cells can be a challenge. The stratum corneum includes layers with lipids that help keep water out. If a molecule’s chemistry is water soluble — meaning it won’t mix with lipids — “it’s going to have a hard time penetrating,” George says.

Other factors that determine how easily a molecule can penetrate the skin include size and polarity, or the distribution of charge across the molecule. Smaller molecules that have the same charge as the stratum corneum’s lipids tend to slip in more readily. In products with in gredients that don’t penetrate easily, such as retinoids, cosmetic chemists can add solvents to aid penetration.

Because different skin care ingredients work in different layers of the skin, application order matters. Dermatologists typically recommend starting with thinner products (think serums) and moving to the thickest (say, sunscreen), because otherwise heavy products could block the ingredients in lighter ones.

If you’re striving for a translucent glow, focus on strengthening your barrier, and add some humectants if you want that moist, glassy look. As King says, “healthy skin looks good.”