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.


METHODS
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.
Department of Exercise Sciences, Brigham Young University, Provo, Utah 84602, USA.
Ulrike H
UH
Mitchell
A Wayne
AW
Johnson
J William
JW
Myrer
Ronald L
RL
Hager
Dennis L
DL
Eggett
D000328:Adult; D004867:Equipment Design; D004869:Equipment Safety; D006358:Hot Temperature / Q000627:therapeutic use; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D007259:Infrared Rays / Q000627:therapeutic use*; D007866:Leg; D016037:Single-Blind Method; D012867:Skin / Q000528:radiation effects*; D012881:Skin Temperature; D055815:Young Adult