Underarm Laser Hair Removal Permanent effect is reached when laser light destroys the hair follicle, and a hair can no longer grow from it. Generally, clients need about two to six laser treatments in order to completely get rid of hair. You can expect to see about a 10% to 25% reduction in hair after your first treatment. As you continue your treatments, more and more hair will fall out. Laser hair removal uses light to target the pigment in individual hairs. The light travels down the shaft of the hair and into the hair follicle to destroy it. As result, a hair can no longer grow.