excessive hair growth affects the healthy population,but it also severely affects patients with hormonal disturbances such as polycystic ovary disease,congenital adrenal hyperplasia,hirsutism,hypertrichosis and congenital hairy nevi.
excessive hair growth has been implicated in the pathogenesis of pilonidal disease and in the unfavourable outcome of reconstructive flaps.
each hair has 3 distinct components: the bulb(which lies near the insertion of the erector pili),the isthmus and the infundibulum.
pluripotent cells in the bulb and the bulge areas cause growth of the hair follicles. melanocytes are present in these areas,for most people,the bulb is approximately 4mm beneath the surface of the skin (deeper in some individuals). therefore, a considerable laser penetration depth is required to remove the bulb.
hair grows in cycles. anagen in the active growth phase,catagen is the transition phase and telogen is the resting phase.the duration of the anagen phase governs the length of hair at different body sites. lasers are truly effective in only anagen phase, when hair matrix cells divide rapidly and migrate outward from the shaft and when the melanin ia at its highest. during the catagen phase,mitosis ceases, the hair matrix regresses, the papilla retracts to a place near the bulge, and capillary nourishment diminshes. in the telogen phase, the follicle detaches from the papilla and contracts to a third of its original depth,eventually falling out. the telogen phase varies in duration from one body to the next.
the ratio of anagen follicles to telogen follicles varies with body location. because not all the hair are in the anagen phase at any time, laser treatment must be repeated to capture the new hairs coming into the anagen phase.