Why are multiple treatments necessary in laser hair removal?

Multiple treatments are necessary in laser hair removal primarily because not all hair follicles are simultaneously in the optimum growth stage, which is known as the anagen phase. Hair grows in cycles, including growth, rest, and shedding phases. The laser is most effective on hair that is actively growing, as this is when the pigment in the hair absorbs the laser energy most effectively.

During any single treatment, only a portion of the hair follicles are in the anagen phase. Those hair follicles that are in the resting phase (telogen or catagen) do not respond to laser treatment in the same way, as they lack the necessary pigment and structural characteristics that make them susceptible to the laser's energy. This is why multiple sessions are essential; each treatment can target hair follicles that were in different growth stages during previous sessions. This cycle of treatment allows for the comprehensive reduction of hair, achieving more effective lasting results over time.

Other factors such as skin type, hair color, and hormonal influences can affect hair growth and laser effectiveness, but the primary reason for multiple treatments remains the timing of the hair growth cycles.