Teosyal RHA 4 is a transparent, sterile, injectable hyaluronic acid dermal filler used to restore volume to the skin or augment facial features. It is comprised of of cross-linked hyaluronic acid of non-animal origin, as well as lidocaine hydrochloride (an anesthetic). Teosyal RHA 4 may only be injected into deep wrinkles, scars, or other depressions by authorized medical professionals.