How Does Laser Hair Removal Work?

Shaving my legs is such a drag! I'm thinking about trying laser hair removal. How does the procedure work?

Oct. 9, 2000 -- Yes, it works -- but only for some people. And contrary to popular belief, a few zaps of a laser doesn't mean you can totally retire your razor. What the laser can do, however, is to reduce the amount of hair you have and, perhaps, lead to some permanent hair removal. In addition, it can lighten the color of the hair and decrease its thickness.

Laser hair removal takes about an hour for both legs. As the laser is moved over your legs, the light passes through your skin and gets absorbed by the melanin (pigment) in the hair follicles. Although no one knows exactly how lasers reduce hair growth, the most popular theory is that the heat generated by the laser breaks apart the follicle. Over the next two months, hairs gradually fall out. For most people, the pain -- similar to a rubber band snapping on the skin -- is quite tolerable. If you're very sensitive, however, your doctor can apply a topical anesthetic cream to numb the area.

Before you sign up for laser hair removal, though, take into account your natural hair and skin color, as the treatment tends to work best on fair-skinned people with dark hair. If you're tan or have a darker skin tone, the laser gets absorbed by the pigment in the skin and doesn't reach the hair follicle, limiting the effect of the treatment and potentially damaging the skin. The procedure doesn't seem to work very well on light-haired people either, whose hair contains little melanin.

You should keep in mind that three or four treatments, six to eight weeks apart, may be needed to achieve a meaningful reduction in the amount of hair on your legs (or elsewhere). After that, you'll need to wait a year to see the full effect of the treatment (hair growth cycles are about six months long, so it's best to wait through two growth cycles to see the final results).

Since the area treated will be extremely sensitive for a few days, it is wise to wear both protective clothing and sun block whenever you're outside. In addition, plan to limit your sun exposure for a day or two after the treatment, as you can expect some slight swelling and redness. These side effects should disappear within a day and can be soothed with ice or a mild anti-inflammatory cream. More rare side effects include peeling, blistering, and burning of the skin as well as brown spots and slight loss of pigment in areas where the laser has been used.

Nelson Lee Novick, MD, FACP, FAAD, is an associate clinical professor of dermatology at Mt. Sinai-NYU Medical Center in New York. He is the author of several skin care books including Super Skin: A Leading Dermatologist's Guide to the Latest Breakthroughs in Skin Care.