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Hyaluronic Acid: What It Is and How It Works

Droplets of a hyaluronic acid serum for skin

Hyaluronic acid has a good reputation—understandably so, as it’s one of the most effective ingredients for moisturizing skin out there. But while its moisturizing abilities are well-known, how it works is a little less so. And the more you learn, the better you can maximize its benefits.

What is hyaluronic acid?

First, the basics: Hyaluronic acid, a molecule found naturally in the body, is a humectant. That means “it retains moisture within the skin,” explains Dendy Engelman, M.D., a dermatologist in New York City. “Think of it as a magnet.”

How hyaluronic acid works

Once it sinks into skin, hyaluronic acid (which sometimes goes by the moniker sodium hyaluronate) can hold up to 1,000 times its weight in water—and in doing so gives skin a soft, plumper texture and more even skin tone. “It can improve fine lines and wrinkles as well,” says Engelman. On top of that, hyaluronic acid is gentle on the skin barrier, making it a good choice whether you have dry or dehydrated skin.

Why size matters

But not all hyaluronic acid molecules are created equal. In fact, there are six different sizes. “Different molecular weights penetrate to different levels of the skin,” says Engelman. Molecules with lower molecular weight are smaller, and can therefore reach the deeper layers of skin. There, they sustain skin’s moisture content. Those with high molecular weights, on the other hand, remain closer to the surface, where they can deliver the most visible results—that is, softer, smoother, and firmer skin.

The best way to use a hyaluronic acid serum

Though hyaluronic acid can attract and retain moisture, it doesn’t necessarily keep that moisture from evaporating over time. That’s why it’s important to maximize the benefits by adding an occlusive or emollient ingredient into your routine, like a face oil. It seals in the moisture drawn into skin by the hyaluronic acid, and the two work together to ensure skin is both hydrated and stays that way.

Still, skin loses hydration with age, according to Engelman. On top of that, “hyaluronic acid has a short half-life and is unstable, making it easy to be degraded by other factors,” she says. To offset this inevitable moisture loss—and therefore minimize dryness, lines and wrinkles, and other signs of aging—it’s important to incorporate it into your daily routine to ensure you can reap all of the benefits.