Further Investigation of Pigmentary Changes After Alexandrite Laser Hair Removal in Conjunction With Cryogen Spray Cooling

Extent of lateral epidermal protection afforded by a cryogen spray against laser irradiation

“…For the subject's skin phototype and the CSC and laser parameters considered herein, there is a ring/crescent-shaped mismatch between cooling and heating irradiating over an 18 mm diameter area, Figures 6b and 7a. As proposed previously [24], increasing the spurt duration can enhance the extent of lateral epidermal protection afforded by CSC: Figure 7b shows that a 60/ 30 milliseconds cooling sequence provides for more skin protection than 50/50 and 50/30 milliseconds sequences. Adjusting the time delay between CSC and irradiation can also enhance protection [8]: Figures 6b and 7a show that a 50 milliseconds delay resulted in more crusting as opposed to using a shorter 30 milliseconds delay.…”

“…Dyspigmentation by cooling is unlikely because the drop in temperature at the sprayed zone periphery is insignificant, Figure 2a. Kelly et al [23,24] demonstrated experimentally that there is risk of thermal injury if the spurt duration is too short, the handpiece is not held perpendicular to the skin surface, or the cryogen nozzle is misaligned. Furthermore, even if these situations could be avoided, the results of the latter investigation showed that there is also a risk of skin injury by excessive heating if there is a mismatch between the skin surface protected by CSC and that exposed to laser irradiation.…”