Hyaluronic Acid Supplement. Hyaluronic acid is a polysaccharide (a large sugar molecule) found in all animal species and in all tissues. Its function is to absorb and retain water to maintain skin hydration. The passage of years and sun exposure are the cause of skin aging, due to a decrease in hyaluronic acid. In cosmetics, this protein is particularly indicated for preventing epidermal dryness of the face, neck, and décolleté.