It is impossible to give an exact number of treatments required since the anatomy and biology of the hair bulb differs in individual patients and in different anatomic areas. For example, on the scalp 80% of the hairs are in the growing mode and 20% are in a resting mode. Hairs can only be effectively treated when they are in the growing or anagen phase. On the eyebrow 80% of are in the resting phase and only 20% are in the growing phase. Likewise, chin, back, bikini line and axillae all have different ratios of hair in the growth and resting phase and the rate that these hairs turn over to complete the hair cycle differs. Furthermore, the depth of the hairs varies between anatomic areas. In certain areas, such as the back, the hairs are deeper.
When hairs are treated during the growth phase a good proportion can be permanently removed. However, further hairs will regrow. The hairs should be treated at the first sign of hair regrowth or at 2 month intervals. Eventually, after several treatments (depending on the patient and anatomic area) any hairs that regrow will either be so fine or so few that essentially further treatments will not be necessary. Therefore, the term permanent hair reduction is the goal of therapy and a patient can determine the endpoint in terms of when they are satisfied with their progress.