Laser hair removal can be a costly but effective way to get rid of the unwanted hair people are sick of shaving, trimming or waxing.

But spending thousands of dollars on the required treatments doesn’t always guarantee body hair will be gone for life. Below, plastic surgeons and dermatologists detail how laser hair removal works, how much it costs and just how long it lasts.

How does laser hair removal work?

“The laser light is directed at and gets absorbed by the pigment in the hair itself, which sits in the hair follicle,” said Dr. Robyn Gmyrek, dermatologist at Union Square Laser Dermatology in New York City. “When the laser light gets absorbed, it creates heat. If enough heat is generated down the hair follicle, it will destroy the hair growth center in the follicle. If the hair growth center is destroyed, you should not create a new hair.”

Gmyrek explained that body hair goes through a resting and growth cycle, which is why a series of follow-up treatments are scheduled every 4-6 weeks.

“When the hair is in a resting portion of the cycle, it may not be able to absorb enough laser light or generate enough heat to destroy the hair growth center,” she said. “This means is that you have to laser multiple times -– usually about 6 sessions ? to remove a substantial portion of the hair from an area.”

Treatment can be costly.

Treatment costs, methods and effectiveness depends on each person’s skin type, hair thickness and the area being lasered off.

“No matter what area you are treating, usually about 6 treatments are needed to achieve approximately 80 percent clearance. This is based on the cycling of the hair,” Gmyrek said.