Ruby laser-assisted hair removal - correlation of efficacy with the growthcycle of human hair

There is great variation in response when ruby laser is used to remove unwa nted body hair. Destruction of hair is often not possible after one laser t reatment and the frequency and timing of repeated treatments required to ac hieve optimum treatment results are unknown. It was the aim of this study t o determine whether the efficacy of ruby laser hair removal depended on the hair growth cycle. A prospective clinical study was carried out. The lower legs of 38 patients were treated with the Chromes 693 ruby laser at a stan dard fluence of 11 Jcm(-2). Treatment efficacy was determined as the percen tage decrease in hair density at 3 and 7 months. The proportion of growing and resting hairs in the treatment site was assessed by examination of pluc ked hair roots harvested from areas adjacent to the treatment site. To dete rmine whether examination of plucked hair roots microscopically was reliabl e in assessing the proportion of growing and resting hairs in a specific si te. 7 ex-vivo scalp skins were examined histologically. Results showed that examination of plucked hair roots was a reliable method in assessing the p roportion of growing and resting hair. There was no correlation between the treatment efficacy and the growth phases of hair (one way analysis of vari ance, P=0.116). In conclusion, growing hairs are not more susceptible than resting hairs to ruby laser injury. The clinical implications of this findi ng are discussed.