A case series of 15 patients published in July 3, 2020 in Lasers in Surgery and Medicine identified the cause behind a unique adverse event seen following laser hair removal in three clinics. In the paper, Abdulmajeed Alajlan MD, looked at the cases of 15 patients who experienced crescent-shaped areas of post‐inflammatory hyperpigmentation (PIH) following laser hair removal procedures. What he discovered was misalignment between the laser beam and cryogen spurts.
The retrospective, multicenter study included patients from three laser centers with crescent‐shaped PIH following laser hair removal. Dr. Alajlan found that all patients were treated with the GentleLase system (Candela) with built‐in cryogen spurt. Prior to the study, only one patient had suffered from PIH following laser hair removal, and, in the majority of cases, the PIH resolved on its own with and without the use of bleaching compounds. After testing one of the laser devices, he found that the cryogen spurt was misaligned. Because it was not located in the circle of the laser beam, it left a crescent shape of skin treated but not cooled, resulting in PIH.