What is hyaluronic acid (HA) used in some injectable dermal fillers?

Hyaluronic acid or HA is a complex sugar that occurs naturally in the skin. The substance keeps the skin hydrated and plumped, and, when used in fillers, is gel-like and soft. Most HA filler products are infused with lidocaine to minimize any discomfort during and after treatment. HA fillers last about 6 to 12 months, on average.