Today's skincare-savvy spa clients understandstand that for long-lasting, obvious wrinkle reduction, it's important to couple trips to the spa with visits to the dermatologist. While estheticians have many powerful anti-aging tools at their disposal, few offer the same benefits as prescription topical products or injectables. That said, there is one ingredient that is found in both in-office injectables and spa services: hyaluronic acid. This potent component may be just what your clients' complexions are craving.

So what exactly is hyaluronic acid? Also known as hyaluronan, hyaluronate, or more commonly, sodium hyaluronate (which is the form often used in topically applied skincare products), it is a component of connective tissue that is found throughout the body but mainly in the joints and lower layers of the skin, and its key function is to cushion and lubricate cells. In the dermis, it's found between skin cells, where it has a protective function and is also involved in tissue repair. "Hyaluronic acid has been named as a key to youth and is a very important anti-aging ingredient," says Jeanette Graf, M.D., a Great Neck, NY-based dermatologist. This explains why it is the main ingredient in anti-aging injectables like Restylane, Perlane, and Juvederm, which help plump and add volume to the skin in order to fill in fine lines and wrinkles. Originally, the hyaluronic acid found in many skincare products, both over-the-counter and dermatologist-prescribed, was derived from animal sources—rooster combs to be specific—but most is now synthetically created.

The protein has been praised for many reasons, one of which is its potent water-retaining powers, with experts saying it's able to hold 1,000 times its weight in water. Because the powerful humectant hydrates by drawing in moisture from the environment and locking it into the skin, it's a great ingredient to use on clients with breakout-prone complexions. "When I see acneic skin that's dehydrated from overuse of stripping agents, I can safely use products with hyaluronic acid in them because it provides moisture without stimulating the sebaceous glands the way things like shea butter and nut and plant oils can," says Annet King, director of training and development for Dermalogica's International Dermal Institute. King points out that most hyaluronic acid products also have a light texture that's especially pleasing to those with oilier skin.

Hyaluronic acid's hydrating nature also makes it perfect for mature skin treatments. As we age, the body's natural storage of hyaluronan is depleted. For women moving into or going through menopause, there's even less to go around, as estrogen stimulates hyaluronan production. This is part of the reason why skin can look visibly parched and crêpey during its later years. While it's important to let clients know they shouldn't expect the same benefits from topical products that injectables are able to offer, spa treatments that use products with hyaluronic acid can leave complexions looking and feeling firmer. At Spa Gaucin at the St. Regis Resort (Dana Point, CA), guests who receive the Antioxidant Wine Therapy Facial ($175, 60 minutes) rave about how fresh and rejuvenated their skin looks. The treatment involves a cleansing enzyme exfoliation and an application of a mask that contains hyaluronic acid. "Many of our guests are seeking plumper skin with less visible lines, and they love the immediate results they see after this treatment," says spa director Valory Reed.