The laser is attracted to the dark pigment in hair called melanin. The energy from the laser travels down to the base of the hair follicle using melanin as a ‘conductor’ where it disperses as thermal energy. This damages the base of the hair follicle rendering it unable to produce hair as quickly. This rate of growth will decrease more as you have further treatments.
As well as the laser needing melanin, the hair must also be in a certain stage of its growth cycle for the treatment to be effective. This cycle is known as the ‘active growing phase’, or anagen, and is when the hair is connected to the base of the hair follicle. This connection provides a direct pathway for the laser energy to disperse where the hair is produced at the base of the follicle.
Not every hair is in this phase at any one time on the body which is why you will need multiple treatments. This is referred to as the ‘resting phase’ or telogen.