Effect of infrared and red monochromatic light on equine wound healing

Light-emitting diodes (LEDs) are commonly used for treating a variety of disorders in horses, including wounds. Despite its claim to shorten healing times, there is a lack of scientific documentation regarding its effects.

To investigate if treatment with pulsating visible red light (λ ≈ 637 nm) and near-infrared (NIR) light (λ ≈ 956 nm) affects wound healing.

Randomised blinded controlled experimental study.

A circular skin wound (Ø = 2 cm) was created on each side of the neck in eight healthy horses. One randomly chosen wound received light treatment and the other served as an untreated control. Treatment duration was 4 minutes and 40 seconds (red light 95 seconds, 2.3 mW/cm² ; NIR light 185 seconds, 6.4 mW/cm² ) and was performed once daily on day 0-4, 7-11, 14-18 and 21-25. The wounds were photographed and evaluated using digital photoplanimetry on day 0, 1, 2, 3, 4, 7, 14, 21, 28 and 35. The degree of swelling was assessed with diagnostic ultrasound on the same days except the last recording was performed on day 36 instead of 35. Days to total healing was recorded. ANOVA was used for statistical analysis (P < .05).

The wound area (P = .2-.9) and degree of swelling (P = .2-1.0) did not differ between treated and control groups on any day. There was a significant difference (P = .03) in healing time between control (49.0, 95% CI = 35.4-62.6 days) and treated wounds (51.8, 95% CI = 38.7-64.8 days).

The wounds were treated until day 25 and this study does not investigate the effect of a longer treatment period than 25 days.

The results of this study do not indicate any clinically relevant positive effect of pulsating visible red light and NIR light on the healing of experimental skin wounds in horses, compared with no treatment.