The method is based on absorption of light by the melanin pigment in the hair follicle. Light energy absorbed in the follicle is transformed to heat which coagulates the follicle. Treatment parameters have to be optimized for each patient skin type, hair color, thickness and density in order to maximize treatment effectiveness and minimize damage to surrounding skin. Only follicles in the active growth phase have enough pigment to absorb the light and reach necrosis temperature. The average growth of hair is about 0.35mm a day, but this varies depending on the area of the body, age and gender. Approximately 20-25% of hair follicles on the body are in the growth phase at any given time. This represents the percentage of hair follicles that can be destroyed in a single treatment session. In order to eliminate up to 70% of the hair, treatment has to be performed a number of times until the desired result is achieved. The typical series of treatments is 7-10 treatment sessions, spaced 4-8 weeks apart depending on the area being treated.