Why are multiple treatments necessary for effective laser hair removal?

Multiple treatments are necessary for effective laser hair removal primarily because hair grows in different phases, specifically the anagen, catagen, and telogen phases. The laser is most effective when targeting hair during the anagen phase, which is the active growth stage. Not all hair follicles are in the same phase at any given time, meaning that multiple sessions are required to ensure that all hairs can be effectively targeted and destroyed.

During a single treatment, only a fraction of hair may be in the appropriate growth phase to be successfully treated. As a result, spaced-out treatments over several weeks or months allow for optimal targeting of hair as it moves through its growth cycles. This process ensures a more permanent reduction in hair growth compared to a single session, which would miss many of the hairs not yet in the correct phase for effective treatment.