why a single laser session can’t remove all the hair ?

To understand why multiple sessions are necessary, it helps to look at the science behind hair growth. Each hair follicle goes through three main phases:

Anagen (active growth phase) – This is when the hair is still attached to the follicle and is most responsive to laser energy. The laser targets the pigment (melanin) in the hair shaft, which transfers heat down into the follicle to disable future growth.

Catagen (transition phase) – In this stage, the hair begins to detach from the follicle. Because the connection is weaker, the laser can’t effectively destroy the root.

Telogen (resting phase) – The hair has fully detached and will soon shed naturally. Follicles in this stage are inactive and will only start producing a new hair later.

At any given time, only a percentage of your hair is in the anagen phase. This is why a single laser session can’t remove all the hair in a treatment area. Multiple sessions are needed to catch each follicle during its active growth phase, when the laser can have the greatest impact.