What is hyaluronic acid and how does it hydrate skin?

Hyaluronic acid is a humectant naturally found in the skin that can hold up to 1,000 times its weight in water. In skincare, it draws moisture from the environment and deeper skin layers to the surface, plumping and hydrating skin temporarily. For best results, apply it to damp skin before sealing with a moisturizer, as applying it to dry skin in low-humidity environments can actually draw moisture out of the skin.