The effect of ruby laser light on ex vivo hair follicles: Clinical implications

Several clinical studies on the efficacy of ruby laser-assisted heir remova l have reported that regrowth of hair after treatment is common. One of the reasons for the regrowth of hair is the incomplete destruction of germinat ive hair cells due to the insufficient penetration of the ruby laser in the skin. It was the aim of this study to estimate the extent of damage to the hair follicles after one ruby laser treatment and to determine whether the ruby laser destroyed the bulbs and the bulge regions of hair follicles. Th e extent of laser damage in hair shafts was determined by serial examinatio n of six specimens of ex vivo scalp skin lasered with the Chromes 694 Depil ation Ruby Laser at 14 J per square centimeter and 20 J per square centimet er. Another nine specimens of ex vivo scalp skin were similarly lasered, an d monoclonal antibody LP2K was used to identify the bulge regions of the ha ir follicles using the immunoperoxidase technique. Damage to the bulge regi on was assessed from consecutive specimens, which were stained with hematox ylin-eosin stain. The mean depth of laser damage sustained by hair follicles was 1.34 mm (14 J per square centimeter) and 1.49 mm (20 J per square centimeter) underneat h the skin surface. Most of the laser damage involved the bulge regions but fell short of the hair bulbs. The laser damage did not seem to extend far enough down the hair shafts to result in permanent hair destruction. The cl inical implications of this finding are discussed.