The back is hard to manage alone, which makes laser especially convenient.
Laser energy is absorbed by the dark pigment in the hair and at its root, turning into heat that damages the structure driving growth. It only works on hair that is growing now, so sessions repeat in step with the hair cycle. The back is hard to manage alone, which is why laser suits it.
It takes about six to eight sessions at four to eight week intervals. The laser only responds to hairs currently growing, and hairs grow on different cycles, so not all are caught in one pass. Regrowth visibly drops from the third to fifth session, and the back is hard to manage alone, so satisfaction is especially high.