Laser Hair Removal&Permanent Hair Reduction

Each hair has 3 distinct components: the bulb, which lies near the insertion of the erector pili, the isthmus, and the infundibulum.

Pluripotential cells in the bulb and bulge areas cause growth of the hair follicle. Melanocytes are present in these areas. For most people, the bulb is approximately 4 mm 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 is 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 the anagen phase, when hair-matrix cells divide rapidly and migrate outward from the shaft and when the melanin load is 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 diminishes. In the telogen phase, the follicle detaches from the papillae and contracts to a third of its original depth, eventually falling out. The telogen phase varies in duration from one body area to the next. For example, the telogen phase may last as long as a year for hair on the leg.

The ratio of anagen follicles to telogen follicles varies with body location. Because not all of the hairs are in the anagen phase at any 1 time, laser treatment must be repeated to capture the new hairs coming into the anagen phase.

The timing of treatments is important because hair should be treated during the anagen phase. This phase is short (6-12 wk) for hair on the head, and treatments are spaced a month apart. On the trunk, the telogen phase lasts 12-24 wk, and 2-month spacing is best.

Author: Mounir Bashour, MD, CM, FRCS(C), PhD, FACS, Assistant Professor of Ophthalmology, McGill University; Clinical Assistant Professor of Ophthalmology, Sherbrooke University; Medical Director, Cornea Laser and Lasik MD