Efficacy of lasers and light sources in long-term hair reduction: a systematic review

Laser and light-based devices provide scope for long-term "hair-removal" however, there is limited evidence supporting their long-term efficacy. This study aimed to assess the long-term efficacy of laser and light-based "hair-removal" devices, taking into account variations in body site-specific variations in hair growthcycles. A systematic review of randomized controlled trials (RCTs) with follow-up periods greater than or equal to the length of one complete hair growth cycle in the body site targeted was conducted. Only five eligible RCTs were identified as suitable for inclusion, and these comprised a total of 223 patients. The average long-term hair reduction reported for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser ranged from 30 to 73.61%, Alexandrite laser ranged from 35 to 84.25%, and Diode laser ranged from 32.5 to 69.2%. In all three devices, the greatest long-term reduction was observed from trials targeting leg hair (1-year growth cycle) and lowest from targeting facial hair (6-month growth cycle). Intense pulsed light (IPL) produced average long-term hair reduction of 52.7-27%; smallest reduction was observed from targeting the face area and greatest from targeting the axillary area (7-month growth cycle). In conclusion, greater long-term hair reduction was observed on body sites with longer hair growth cycles. Future trials should take into account the variation of hair growth cycles across body sites to provide accurate long-term data on treatment outcomes.