Hyaluronic acid is a sugar molecule that occurs naturally in skin and helps it hold water. In skincare it works as a humectant — it draws and binds moisture, hydrating the skin and giving a temporarily smoother, plumper look.
It suits most skin types and pairs well with other ingredients. Apply it to slightly damp skin and seal with a moisturizer, especially in dry environments, so it pulls water into rather than out of the skin. It hydrates the surface but does not replace collagen. See anti-aging skincare routine.