Red Light and Infrared for Horses: What the Wavelengths Do

Photobiomodulation devices deliver light at specific wavelengths – usually 660 nm, which is visible red and penetrates a few millimetres, and 850 nm, near-infrared, which reaches deeper tissue. LEDs are what most equine products use; class 3B and class 4 lasers are a different category, used under veterinary supervision and with their own safety requirements.

Three numbers decide what a device can do: the wavelengths, the irradiance in milliwatts per square centimetre, and the time. Horseware’s LED pad is specified with 660 and 850 nm, three programmes and cordless operation; the poll cap uses 230 LEDs for the head and neck; the over-reach boot version runs an automatic fifteen-minute cycle. Waldhausen’s Infrared FlexPad combines the same two wavelengths with up to 32 mW/cm², a 38 to 48 °C temperature range and three vibration modes.

The accepted explanation is that light at these wavelengths is absorbed by cytochrome c oxidase in the mitochondria, which increases ATP production and changes local circulation and inflammatory signalling. It is a plausible, well-described pathway in cell and small-animal work.

The step that is harder is the one from the cell culture to the horse’s back, through skin, hair and a fifteen-minute session. That is where the equine evidence has to do the work, and it is uneven.

Wound healing is the best-studied application. Work on equine limb wounds using 635 nm LED light found faster healing than untreated controls, and wounds on the lower limb – where blood supply is poor and healing is slow – are exactly where a small effect is worth having.

Studies on performance horses with orthopaedic injuries have reported analgesic and anti-oedema effects with near-infrared treatment. Read that as short-term comfort and swelling, applied as part of a plan, rather than as repair.

A systematic review of veterinary laser and light therapy published in 2023 found conflicting results between studies and no consensus on protocols: the wavelength, dose and session length that produced an effect in one trial were not what the next trial used. At least one equine trial found no direct effect of infrared phototherapy on wound healing at all.

There is no good evidence that these devices improve performance, activate cells in any way a rider would notice, or replace a diagnosis. A horse that is sore has a reason for being sore, and light does not find it.

Light does not travel through a rug or through mud, so the pad has to sit on a clean coat, and the treated area is only as large as the pad. Manufacturer programmes run ten to twenty minutes for a reason: longer is not proportionally better, and the biphasic dose response described in the photobiomodulation literature means more can do less.

Do not aim high-output LEDs into the eye, yours or the horse’s. Use it for warming up stiff backs, for supporting a rehabilitation plan a vet or physio has set, and for small slow-healing wounds – not for a lameness you have not had looked at, and not for a swelling that appeared overnight. If you are deciding whether to buy one, the sensible order is diagnosis first, plan second, device third.