A water-binding sugar from oats, yeast or mushrooms. A good humectant and film-former; claims that it beats hyaluronic acid or rebuilds skin lack evidence.
Beta-glucans are long chains of glucose found in oat bran, yeast cell walls and mushrooms. On skin they hold water and form a thin, smoothing film, and lab studies suggest they calm inflammation and support barrier repair.
They are used in soothing toners, ampoules and moisturizers. Large beta-glucan molecules mostly stay on the surface, which suits hydration but limits deeper effects.
Evidence consists of lab studies, animal work and small manufacturer studies, often with beta-glucan combined with other ingredients. No robust independent trials establish benefits beyond surface hydration.