The rays emitted by the L600 can only act on those hairs that are in their growth phase. Statistically, in the hair growth cycle of the area being treated, it is estimated that around 20 % of hairs are in their growth phase at any one time. This is why several sessions are necessary.
In addition, certain "resting" hair follicles can become active due to age and hormonal modifications. This is why, depending on the individual, maintenance sessions may be necessary.