Until last month, Lindsay Christiansen, 26, hadn't worn a bathing suit in three years. The San Diego-based flight attendant gained weight after college and felt self-conscious about her increasingly dimpled thighs. "It got to the point where I didn't even want to wear shorts," she says. Then Christiansen heard about a new treatment that combines intensive massage and cool laser light. She signed up at a local spa and, after just a few weeks, saw a big difference: her legs were slimmer and less rippled--and she looked much better in jeans. "Every day, people are, like, 'You lost weight, what are you doing?' " she says.

Christiansen's treatment, TriActive, is the product of a new wave of research into cellulite--part of an overall boom in cosmetic remedies. The orange-peel-like skin that forms around the butt and thighs affects 85 percent of all women over the age of 18. Yet, for a long time, dermatologists had little information about its nature or how to treat it. "Only in the past three years have we really understood what causes it," says Dr. Jaggi Rao, an associate clinical professor of dermatology at the University of Alberta in Edmonton. Doctors now believe that cellulite forms when the skin begins to thin, allowing fat to rise to the surface. As women experience hormonal changes associated with puberty, pregnancy and menopause, fat cells clump together and accumulate in columns. The columns, separated by vertical connective bands called septa, act like stitches in a quilt: they pull down on the skin, causing it to pucker, even as the fat puffs out like stuffing. (Men typically don't get cellulite because their skin is thicker and they lack these vertical bands.)

But don't start dreaming of Brazilian bikinis just yet: there's still no way of permanently getting rid of cellulite. (Liposuction won't work because it targets deeper layers of fat and could cause scarring if used closer to the surface.) But dermatologists say there are improved ways of diminishing it. The newest treatments are TriActive, a machine that combines skin suction with a cool diode laser, and VelaSmooth, which combines suction with a hot laserlike light. (TriActive was approved by the FDA last year; VelaSmooth is seeking FDA approval.) Both are noninvasive and help loosen the septa and improve circulation, say the two dermatologists who tested the devices for regulators. Christiansen's doctor, dermatologist Kimberly Butterwick of La Jolla's Spa MD, conducted a trial of TriActive (about $150 per session) that will appear in an upcoming issue of the Journal of Cosmetic Surgery. After administering 12 twice-weekly treatments, she saw improvements that were "modest but measurable" in her patients: an average 23 percent reduction in cellulite and a 15 percent reduction in thigh circumference (or just less than 1cm). Dr. Tina Alster of the Washington Institute of Dermatologic Laser Surgery in Washington, D.C., and a professor at the Georgetown University School of Medicine, just completed a trial of VelaSmooth (about $250 per session). Of 20 patients, 18 saw an improvement. Of those, thigh circumference shrank an average of .8cm, and the skin appeared smoother. Alster believes Vela-Smooth is an improvement over Endermologie, an older treatment that kneads the skin but does not use laser light. Still, she says, patients need monthly follow-ups to maintain results.

For a less expensive approach, patients can turn to topical creams. They may look like quackery, but dermatologists say creams help firm the skin and diminish the appearance of cellulite--as long as you use them religiously. Look for ones that contain caffeine, which is believed to drain water from fat cells, and retinol, which tones and firms the skin. Yale dermatologist Lisa Donofrio recommends Jergens Skin Firming Moisturizer ($5.99) or RoC's Retinol Actif Pur ($18.99). Rao suggests wearing spandex shorts to bed at night over the cream to help it absorb.

One piece of good news for lazy cellulite sufferers is that working out, good for virtually every other health condition, won't help much. "If you could build enough muscle bulk under that fat, you could stretch it out," says Donofrio. "But there's no muscle in the lateral thigh." For Christiansen, the decision to spend $1,200 on her backside was easy. "A personal trainer might have cost a lot more," she says. Now she can sit back and enjoy her summer--in shorts.