Hyaluronic acid and its use as a "rejuvenation" agent in cosmetic dermatology.

Since 1996, hyaluronic acid (HA) has been launched onto the market in Europe. Since then, different companies proposed their HAs. Biomatrix (NJ, USA) proposes an animal-derived HA (from rooster comb). Q-Med AB (Uppsala, Sweden) and LEA-DERM (Paris, France) are the main companies to have a nonanimal HA. HA is produced by bacterial fermentation from a specific strain of streptococci. HA has no species specificity and theoretically has no risk of allergy. No skin testing is necessary before injecting because HA is a biodegradable agent. To be utilized as a filler agent for improving wrinkles, scars, or increasing volumes, HA must be stabilized to obtain a sufficient half-life. Process of stabilization varies, according to each manufacturer. This explains the differences in longevity and in viscosity of the different products. Several HAs are suitable to fine lines, to deep wrinkles/folds, or to increase volume. A new indication for "rejuvenation" is injection into the superficial dermis and epidermis. The HA (stabilized or not) is not used to fill in but rather to hydrate and finally to rejuvenate the skin. This procedure must be repeated at intervals of a few weeks or months. If HA is the safest filler agent in cosmetic indications today, some rare side effects may appear and must be known to inform patients. Most of these complications are not severe and will disappear when the product is degraded.