Can horses get sunburned?

That is how veterinarian Kristen Slater, DVM, put it in an article for The Horse, which adds that burns show up most often around the eyes and on the muzzle of pale or white-faced horses.

The reason is pigment. EQUUS magazine explains that pink skin has less melanin, the pigment that gives some protection from the sun, so horses with pink skin are the most vulnerable. It also says horses with white markings on the muzzle, such as a blaze or a snip, need extra attention to that area.

I should say up front that I have never sat on a horse, so everything here comes from veterinary and extension sources and from what riders write to us. The white muzzle is the first place the sources tell you to look.

The Horse lists those groups. A national Cooperative Extension article on blistering skin also says pintos and paints are the horses most commonly affected, along with horses that have a lot of white on the face.

The University of Minnesota Extension, in its guidance on caring for horses in hot weather, tells owners to watch for signs of sunburn, especially on white or light-colored areas. That is a useful rule of thumb for a quick look each day: check where the hair is white and the skin underneath is pink.

The sources describe risk by where the pink skin is, not by coat color alone, so look at your own horse. A blaze, snip or bald face is where EQUUS says to pay extra attention.

• Pink skin under white hair, such as a blaze, snip, bald face or white around the eyes.
• Paints, Pintos, Appaloosas, cremellos and other pale-coated horses, per The Horse.
• Hairless pigmented areas, especially around the muzzle, according to the Extension article on skin problems.

The MSD Veterinary Manual says photosensitization happens when something in the animal makes skin more sensitive to ultraviolet light, and that, unlike sunburn, it does not cause skin damage without that triggering substance. The Merck edition of the manual lists horses among the species where it is most commonly observed.

There are different routes to it. The Horse describes a primary form, tied to things like St. John's wort or ragwort, perennial ryegrass or certain medications, and a secondary form that follows liver damage, for example from heavy intake of clover or alfalfa, infections or liver cancer. The MSD manual says liver function should always be checked when photosensitization is suspected. The Extension article adds that the usual culprits are plant chemicals, often from clovers, that get into the bloodstream, and that the skin can look severely burned, with blisters, weeping and cracking.

Sources do not agree on exactly where each one shows. The Horse says photosensitization often affects both pigmented and non-pigmented skin, while the MSD manual says lesions first appear on white-haired or non-pigmented skin and can reach pigmented skin when toxin levels or sunlight are high. The Extension article describes pigmented hairless areas, especially the muzzle, as hit hardest. That disagreement is a good reason not to diagnose this one yourself.

That is EQUUS magazine's advice: blisters, scabs, bumps or other abnormalities may point to something other than sunburn, and it names photosensitization, which may indicate liver disease, and squamous cell carcinoma, a sun-related cancerous growth usually on or near the eyelids.

Eyes deserve their own mention. Dr. Kelly Knickelbein, a veterinary ophthalmologist at Cornell University, suggests looking at a horse's eyes every day for discharge, squinting, cloudiness or eyelid swelling, and acting quickly on any change because many eye signs are nonspecific. Cornell's write-up of her seminar says horses with a genetic predisposition to squamous cell carcinoma, or with non-pigmented skin around the eyes, should wear fly masks with at least 90 percent UV protection.

I am not a vet and neither is this page, so treat all of this as background for the conversation you have with yours. EQUUS says ordinary sunburn is cared for much as you would care for your own: keep the area clean and out of further sun. If you are not sure it is ordinary sunburn, that is exactly the time to ask.

University of Minnesota Extension says that in addition to shade, masks can help protect a horse from sunburn. EQUUS says that for a horse with white muzzle markings, you can choose a fly mask with a flap that extends down the nose, and that sun-blocking fly sheets, hoods and wraps are also made.

Makers state their own numbers. On our listing for the WeatherBeeta Comfitec Luxe Stretch Fly Mask with Ears and Nose, WeatherBeeta says it has 65 percent UV protection and an extended nose panel that adds comfort and UV protection. Its Comfitec Insect Guard mask with ears and nose is listed with 60 percent. Woof Wear's UV Fly Mask with 3D Ears is listed with 60 percent UV protection, and Woof Wear also lists a separate UV Nose Protector for fly masks. The listings I read do not name a test standard for these percentages, so they are the makers' claims, not independent ratings.

Those figures are not the same as the 90 percent level Cornell's article gives for horses at risk of eye cancer or with pale skin around the eyes. I would not read that as a verdict on any mask. It is a reason to ask your vet what level of protection your horse needs before you pick one, and to read each listing for the percentage and for how far the nose coverage reaches.

Fit matters as much as the number. A mask that rubs, slips or covers the nostrils is a problem of its own. Cornell's advice is to take the mask off at least once a day and check the eyes.

It explains that physical sunblocks, such as zinc oxide ointments, form a barrier and are thick, so they work best on hairless areas such as the muzzle. Chemical sunscreens filter specific wavelengths, are thinner and easier to spread.

That is where I would stop and send you to your vet. Which product and how often is a question for them. This page is not telling you what to put on your horse's skin, and sunblock does not replace shade, timing or a mask.

If a burn has already blistered, scabbed or broken the skin, call your vet first before putting anything on it, because it may be more than sunburn.

Minnesota says shade from trees or buildings gives horses relief from the sun, and notes that shade shifts through the day and that buildings can block natural airflow. EQUUS says a horse prone to sunburn may be kept in the barn during peak daylight and turned out after sundown, while also noting that keeping a horse out of the sun entirely is impractical and undesirable.

For a horse that has been diagnosed with photosensitization, the MSD manual says affected animals should be fully shaded or, preferably, housed, and allowed to graze only at night while the condition lasts. That is guidance for the vet to apply, not something to start on your own.

A mask, a nose flap, shade and a smart turnout schedule tend to work together. If you want to see how sheets and masks fit into the rest of summer, read our fly season page, and for hot-weather horse care, our heat wave page. If the itch is the problem, see what sweet itch is.

Our UPF riding shirt page explains how to read the numbers on a sun shirt and what lowers them.