The diode laser works by targeting the pigment in hair follicles. By shaving prior to treatment, the shaft of the hair is shortened, allowing better accessibility for the laser to target the hair root and follicle. If a patient has not shaven shortly before their treatment, it is possible the light energy is not accurately targeting the follicle, making for an ineffective treatment. Additionally, hairs may absorb the light during treatment and leave burn marks on the skin.