Hyaluronic acid is a naturally occurring substance present in all connective tissues, therefore, when injected it is very well tolerated by the human body. Biologically, the main function of hyaluronic acid is to transfer essential nutrients from the bloodstream to skin cells. In addition to its cosmetic applications, hyaluronic acid is injected into joints to relieve rheumatism and other kinds of joint pain. Hyaluronic acid-based dermal fillers are used to add volume to deflated or depressed areas in the skin. Dermal fillers are substances that can be used to improve facial contour as well as reduce the depressions in the skin due to scars, injuries or lines. When injected, hyaluronic acid acts like an inflated cushion to support facial structures and tissues that may have lost volume and elasticity. It also hydrates the skin by bringing water to the surface, which helps give a rejuvenated appearance. Some hyaluronic acid formulations are combined with lidocaine (a local anesthetic), which can provide a more comfortable procedural experience. Its versatility, combined with the low risk of immune reactions, makes hyaluronic acid products a popular option for injectable fillers. Common hyaluronic acid injections are: Restylane®, Restylane Finelines® and Perlane®.