Mary Fisher felt insecure about her body hair as a teenager on Long Island. High school classmates made fun of her sideburns, and even on summer days she wore long-sleeved shirts to hide her arms. “I fantasized about wearing a bikini to the beach without hair on my stomach,” she said recently.

In the winter of 2003, Ms. Fisher thought she was realizing her dream when she, like 923,000 other Americans, underwent the procedure sweepingly referred to as laser hair removal. The procedure, she was told, would safely and permanently remove the hair on her stomach after several more treatments. She felt fortunate to have found a specialist she knew personally – her dermatologist. “He had worked on my skin for two years,” she said. “I trusted that he knew what he was doing.” But despite the widespread availability of these treatments, customers like Ms. Fisher are beginning to understand that if they don’t use highly qualified technicians, the procedure carries a risk of pain, injury, and even death.

Ms. Fisher, now 33, relied mainly on information from a pamphlet the office receptionist handed to her. “It had some diagrams and a pair of before-and-after photographs,” she said. The day of the treatment, she received only one instruction: Apply a thin layer of topical anesthetic cream across the surface of her stomach. Thirty minutes later, she was numb.

As the laser beamed on her stomach, Ms. Fisher felt a sharp pain, like getting burned with a hot iron. She didn’t ask the dermatologist to stop. “I assumed he knew how much laser to apply without hurting me. I thought I was being oversensitive,” she said. When he finished, Ms. Fisher looked at her stomach and was horrified to see rows of circular welts. Most troubling, however, was that on the left side of her stomach, her yin-yang tattoo was now a yin-less lump of flesh. “The last thing I ever imagined was that he would pass a laser over the tattoo,” she said. “Even I knew you couldn’t do that.”

Driving back home on that cold February day, Ms. Fisher kept all the car windows open and her shirt above her chest to relieve the stinging pain. Several hours later, her skin and nerves were still pounding. “It was like the hot iron was still on me,” she said. She slept with a bag of ice, but by the time she saw her dermatologist two days later, the skin was still raw and raised above the surface. She said the dermatologist only gave her an anti-inflammatory cream and told her the reaction was normal. “I sought help elsewhere and never went back,” she said.

Ms. Fisher is one of a soaring number of men and women who go to the doctor to get rid of unwanted hair. In 2005, the American Society for Aesthetic Plastic Surgery reported that more than 1.5 million men and women in America underwent hair removal with a light source device, a 70% increase from 2003. Dr. Lawrence Reed, an Upper East Side dermatologist who serves as the society’s spokesman, said the sharp increase represents evolving device technology, an increasing number of technicians, and a high level of customer satisfaction. There is no regulatory agency that approves doctors for laser hair removal. Patients who want to be reassured can contact the Better Business Bureau to investigate the history of a clinic. A spokesman for the New York Department of State, Larry Sombke, said a laser that has been classified as a nonmedical device can be used by a cosmetologist or aesthetician who holds a valid certificate or license. “Just because the person has a license doesn’t make him or her an expert,” he said.

Like Ms. Fisher, some people may have difficulty discerning between a qualified and inexperienced technician when impulsive desires get in the way of asking critical questions. They also miss a subtle distinction: Light source hair removal permanently reduces hair, but it does not remove it permanently. Though no board officially keeps records of injured clients, Dr. Reed said there are more satisfied customers than injured patients. “Can lasers have problems? Absolutely. The technology is not perfect,” he said. The possible downside of lasers is that it requires multiple office visits, and may irritate or even burn the skin. But, he added, “Laser is the best method available to permanently reduce hair. It’s less painful than electrolysis and more cost effective than waxing.”

Hair normally grows back in three- to four-week cycles and multiple office visits are required to destroy the follicles. But with Ms. Fisher’s treatment, the follicle had never been destroyed because the laser had burnt her skin instead. She consulted the EpiCenter, a group of clinics in New York City and Long Island specializing in Intense Pulsed Light treatments. IPL transmits and distributes multiple wavelengths of light, whereas a laser emits one wavelength. Dana Wachter, a registered nurse and the president of EpiCenter, considers IPL equipment to be the most advanced in the industry. Like the laser, light from IPL devices is attracted to a follicle’s dark pigmentation, turns the light into heat, and destroys the follicle. But unlike the laser, the IPL’s multiple wavelengths can offer a safer, more precise treatment, zapping deeply buried follicles, for example, without burning the skin.”When operated by a skilled technician with at least six months of experience, IPL’s wider range of settings can make the treatment less painful because we can set the light according to the patient’s skin’s needs,” she said. “It allows technicians to customize treatment according to the client’s skin and hair color and texture.”

Had Ms. Fisher consulted experts, she would have learned that many technicians are wary of using anesthetic creams. “Patients need to be able to feel when a laser is burning their skin,” Dr. Harvey Jay, assistant professor of dermatology at Cornell Medical School in New York City, said. “It’s a necessary warning sign that something isn’t right. If done properly, the procedure should not hurt.”

Though Ms. Fisher has not yet worn a bikini to the beach, she said the lesson from her ordeal has been invaluable. “I learned that comfort is an important part of being treated,” she said. “A technician should work hard to earn my trust, not be dismissive of my concerns.”