Derms say these 10 hydrating serums are dry skin’s worst nightmare

Hyaluronic acid acts as a humectant, meaning it holds on to water. “HA is a chain of carbohydrates that has the ability to hold up to 1,000 times its weight in water,” says David Kim, MD, MS, a board-certified dermatologist. “It’s an ingredient that helps your skin look hydrated and plump.”

Nor is there just one form of hyaluronic acid – it comes in different sizes that are able to penetrate different layers of the skin. “Each molecule is assigned a molecular weight, which is inversely related to how deeply the molecule can penetrate the skin,” says Rina Allawh, MD, a board-certified dermatologist at Schweiger Dermatology Group in King of Prussia, PA. The smaller the molecule, the deeper into the skin it is able to penetrate.

It may seem that you always want to go for the hyaluronic acid with the lowest possible molecular weight, but this is not always the case. “The benefit of higher molecular weight hyaluronic acid serums is the anti-inflammatory and soothing properties as it forms a durable film with the top layer of the skin,” says Allawh. “A low molecular weight hyaluronic acid serum is more likely to have a lasting anti-wrinkle and regenerating effect and works at the deeper levels of the skin. As you can imagine, lower molecular weight hyaluronic acid serums are able to lock in the moisture in the skin’s connective tissue and consequently stimulates firming effects.”

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