Beta-glucan can be derived from yeast or oats. It has some antioxidant properties and is a strong anti-inflammatory agent (Sources: Journal of Drugs in Dermatology, February 2007, pages 167-170; and Free Radical Biology and Medicine, February 2001, pages 393-402). It is considered an excellent ingredient for reducing redness and other signs of sensitive skin.

A 2005 study demonstrated how oat beta glucan prompts an auto-immune system response from the body when applied topically, resulting in the synthesis of collagen and a reduction in fine lines and wrinkles. – Source needed, quoted here

Also see: Yeast Beta Glucans.