The 755nm laser wavelength aims to effectively disable unwanted pigmented hair follicles, thus impairing hair growth. When light penetrates the skin it selectively damages the root of unwanted hair (the follicles) and their regrowth ability. The newly grown hair becomes thinner and reduced in quantity. As the reaction between laser energy and biological tissues is short, the risk of thermal injury to surrounding tissues is reduced. GentleLase is FDA clearance.
The laser can only disable hairs in their active growing phase. And since hair goes through different growing phases; therefore, several treatments are required to disable all hair follicles in the treated area.