A randomized single-blind controlled trial comparing two monochromatic near-infrared light devices: implications for tissue heating and safety.

OBJECTIVE:
Use of near-infrared light (NIR) is becoming more commonplace in the treatment of different pathologies; however, its safety in terms of heat generation and penetration has not been documented. The purpose of this investigation was to determine and compare skin surface and underlying tissue temperature response during and for 15 mins after a 30-min NIR application to the posterior lower leg using two different NIR devices (Anodyne and HealthLight) and one sham treatment. With this information, recommendations regarding potential adverse skin reactions, including burns, can be made. In addition, these results can serve as a reference for further studies.
DESIGN:
This single-blind randomized controlled study used a repeated-measures design. Fifteen healthy college-age individuals randomly received 30-min treatments with two different near-infrared devices and one sham device to their lower leg. A thermistor underneath the diode and a thermocouple with temperature sensors at three depths measured the temperature at skin surface and in deep tissues, respectively, every minute during the treatment and for 15 mins posttreatment.
RESULTS:
After 30 mins of treatment, there was a significant temperature increase between the NIR devices underneath the diodes and all tissue depths and the control. The skin temperature underneath the treatment diodes increased about 9.5°C from baseline to 40°C. There was no difference between the tissue temperature changes in response to the irradiation with the two NIR heating devices. A limitation of the study is that the entire sample was drawn from a healthy college population.
CONCLUSIONS:
The surface and underlying tissue temperature heating produced by the two NIR devices is within limits considered safe for healthy subjects.
PMID: 22660375