Background. Laser epilation is based on the principle of selective photothermolysis, absorption of laser energy by the target chromophore melanin. It is claimed that larger spot sizes may be more effective for hair removal at identical fluences.
Objective. To compare the efficacy of 18- vs. 12-mm spot size in hair removal using a Gentlelase Alexandrite laser from Candela Corporation (Boston, MA).
Methods. In this double-blind, randomized control trial, patients underwent laser-assisted hair removal on the axillary region. Regions were randomly selected and treated with either an 18- or a 12-mm spot size. Three treatments at 6-week intervals with a 755-nm Gentlelase Alexandrite laser (Candela Corp., Canton, MA) at a fluence of 16 J/cm2 with cooling and delay times of 60 ms. Hair counts were taken before each treatment session and compared. The mean percentage hair reduction and student's paired t-test were used to compare 18 versus 12 mm versus control sites at each visit and compared it with the baseline hair count.
Results. There was a 10.3% difference in mean reduction favoring the 18-mm spot size treated area at the 6-month follow-up.
Conclusion. Our results indicate that a larger spot size appears to be more effective for laser assisted hair removal.