Laser hair removal requires more than one treatment because hair grows in cycles. For the treatment to be effective, the strand must be in the anagen phase of its growth cycle to impair it enough that hair will not regrow. In addition, not all follicles are in the same growth phase simultaneously, so multiple treatments are required. On average, after 8-10 treatments, 80-90% of unwanted hair will be eliminated, and you can treat any subsequent hair growth with a touch-up treatment as needed.