The most commonly used dermal fillers are made up of a hyaluronic acid. These gels are injected into soft tissues under the skin to help restore volume and fill in lines. Hyaluronic acid is naturally produced by the body, and functions to retain moisture to keep your skin hydrated. Similarly, some hyaluronic dermal fillers can be injected into superficial layers of the skin to draw moisture and hydrate the skin from within. Think of it as a long-lasting moisturiser that only needs to be reapplied once in a few months.