Summer is easily a horse keeper’s favorite season—what’s not to love? The rainy, muddy spell of spring has passed, the longer days allow plenty of time to ride, and your horse’s coat is sleek and easy to clean. Sure, it can get hot, but you can always stay indoors to keep cool while postponing the barn chores for the more temperate evenings.

If our horses could tell us what they think, however, chances are they’d give summer a much less favorable review. For every reason we love summer, there are at least two why the season is especially hard on them. From hooves that crack from stamping in response to flies to a body type that holds heat more efficiently than it disperses it, horses simply aren’t designed for summer weather.

This means that you need to be vigilant in caring for your horse this season. You’ll need to be aware of the health problems summer can bring so you can identify them early and take action to protect your horse. Of course, the specifics of the season will vary by location, but there are some nearly universal concerns. Here’s a quick look at some of the conditions that could adversely affect your horse’s well-being this summer.

1. Anhidrosis

Description: Anhidrosis is the inability to sweat. The exact cause is still unknown, but it’s thought to be related to prolonged stimulation of the sweat glands, particularly in very hot, humid conditions. This causes the horse’s thermoregulatory system to essentially shut down. Horses who cannot sweat overheat with even slight exertion in warm weather.

How you’ll recognize it: An anhidrotic horse will remain dry when those around him are sweating. He may also show signs of heat stress because he’s unable to cool himself. You may be able to catch the condition early if you notice your horse is sweating less than he used to or less than the temperature and situation seem to call for. Consult your veterinarian for a diagnosis.

What you can do:There is no proven cure for anhidrosis, although some owners and veterinarians have had luck with supplements formulated to treat the condition.

The surest way to help an anhidrotic horse is to move him permanently to a cooler climate. Many can function very well and may even resume sweating after a few years. If you can’t move an anhidrotic horse, you’ll need to keep him as cool as possible with stall fans and water during the summer months and forgo any riding. 

2. Bruised hooves

Description: Like your own skin, a hoof bruises when blunt-force trauma causes blood vessels within to rupture and leak. In summertime, hoof bruises are most commonly caused by fast work on parched, hardened footing or repeated stamping in response to flies.

How you’ll recognize it:A horse with hoof bruising is likely to be “footsore” and tender, particularly on firm footings. Pay attention if your horse starts taking shorter strides or is reluctant to walk on surfaces he used to traverse without hesitation. Bruises can sometimes be seen on the clean sole of a newly pared hoof. If the hoof capsule cracks and bacteria enter, a bruise can turn into an abscess, and the horse will become dramatically lame as pus accumulates and has nowhere to dissipate inside the rigid hoof wall.

What you can do: Keep it slow on hard ground—only walking and trotting if hoofbeats “ring” as you travel across it. If your arena footing is “dead,” consider upgrading it as an investment in your horse’s long-term soundness. To control fly-stamping, outfit your horse with fly control products that target the legs, such as repellent bands or fly wraps.

Whatever the cause of the bruises, hoof pads or hoof boots may also help protect your horse’s feet. Talk to your farrier about options that might work well for your horse and environment.

3. Conjunctivitis (pinkeye)

Description: Conjunctivitis is swelling of the membranes around a horse’s eye, caused by an infection. It occurs when trauma to those tissues opens the way for bacterial invasion. In one common summertime scenario, face flies gather around a horse’s eye, attracted to the moisture. To rid himself of the irritation, the horse rubs his eye on his knee. The insects leave, but any bacteria they were carrying are rubbed into the sensitive eyelid membranes. Windblown dust can also cause irritation and rubbing, leading to conjunctivitis. Unlike pinkeye in people and cattle, conjunctivitis in horses is not contagious.

How you’ll recognize it: A horse with conjunctivitis has swollen eyelids, perhaps with angry-looking pink membranes protruding through the lids. The eye may also be weepy and runny. If you pry open the lids, you’ll see a normal, clear globe below. This is important to help distinguish conjunctivitis from other, much more serious ocular conditions such as uveitis or fungal infections. Likewise, a horse with conjunctivitis won’t be sensitive to light, whereas a horse with a more serious eye condition likely will be.

What you can do:The best prevention for conjunctivitis is a well-fitted fly mask worn continually. Not only will this keep insects away, but it will also cut down on the dust that blows into your horse’s eyes. Also work to reduce the fly population on your farm with sensible manure-management practices and perhaps the use of parasitic wasps that can kill fly larvae before they hatch. If your horse does develop conjunctivitis, the treatment is topical antibiotic eye ointment, which your veterinarian can prescribe. A farm call may also be in order to verify it is simply pinkeye and not something much more serious. It’s money well spent to protect his vision. 

4. Dehydration

Description: From a purely physiological standpoint, dehydration is a deficiency of fluid within an organism. But it’s much more than your horse just being thirsty. Dehydration can cause serious health problems, such as impaction colic, and become a complication of other conditions. Dehydration can occur any time of year, but it is common in summer when fluid loss from sweating outpaces a horse’s intake through drinking.

How you’ll recognize it: A dehydrated horse will be lethargic, with dry, sticky mucous membranes and “sunken” looking eyes. You’ll want to notice dehydration long before it reaches this point, however; the best way is to use a skin-pinch test: Grab a fold of skin on the point of the shoulder (not the neck as you may have been taught years ago) and pull it away from your horse. Let the skin go and count the seconds until it is flat again. In an adequately hydrated horse, it will snap back in one or two seconds. Any longer indicates dehydration, and a delay of six to 10 seconds warrants a call to your veterinarian.

What you can do: Make sure your horse has fresh water available at all times. And don’t believe the myth that drinking after work causes tying up or colic—it doesn’t. If you add electrolytes to your horse’s water, offer a second bucket of plain water so he has the option to drink that as well.

If you worry your horse still isn’t drinking enough, encourage him by flavoring his water with a splash of apple juice, or offer him watermelon slices—a trick used by endurance riders to increase intake. If your horse resists all your efforts to entice him to drink, call your veterinarian. 

5. Equine insect hyper-sensitivity (sweet itch)

Description: This is an allergic reaction to the saliva of tiny biting midges (Culicoides spp.). The reaction can occur anywhere on a horse’s body but most commonly appears on the belly, root of the mane, base of the tail and face. The horse develops intense itchiness in those areas, which can cause him to rub them so much he damages the skin. Certain breeds seem to be more genetically susceptible, including Welsh Ponies, Icelandic Horses and Shires.

How you’ll recognize it: A horse with sweet itch develops crusty, inflamed, hairless patches of skin on the affected areas. He’ll also be obsessively scratching those spots, rubbing them on fences, tree trunks, the ground and anything else he can.

What you can do:First, shield him as much as you can from insects. A variety of fly-proof garments, some of which wrap around the entire belly and tail head, can go a long way toward protecting your horse. Fly sprays also help, but make sure they are repellents and not simply insecticides, which may kill only after flies have bitten and done their damage. Finally, you can adjust the turnout schedule to keep your horse indoors at dawn and dusk, when the midges are most actively feeding. If he can spend those hours in a stall with screened windows and doors, even better.

If management changes alone don’t seem to be helping your horse, make an appointment with your veterinarian to discuss other options. Medications such as corticosteroid shampoos and injections can help stop the inflammatory reaction. 

6. Heat stress/exhaustion

Description: Horses evolved in cooler climes, so they are built to hold heat to stay warm. While this serves a horse well in the winter, during the summer months it can cause his internal body temperature to rise quickly, especially when he exerts himself. When his temperature reaches 104 degrees Fahrenheit, his metabolic system cannot function properly. At 105 degrees his organs shut down and circulatory collapse that can ultimately lead to death sets in.

How you’ll recognize it: A heat-stressed horse will sweat profusely across his shoulders, neck, rump and lower legs; moisture will drip off his belly. In extreme cases, he may stop perspiring because his system is so stressed. He may also “pant” in an effort to dissipate heat as a dog would, or he may breathe very deeply and fast. He may have a “dull” demeanor as if he’s preoccupied, or he may be in a frantic state and nearly panicky.

What you can do:Stop working your horse immediately. Douse him with cold water and scrape it off to facilitate cooling evaporation. There is no harm in putting cold water on hot muscles. In extreme cases, apply ice packs to his face and throat—places where blood is close to the surface and can be cooled. Keep him in the shade and offer him water. If the horse doesn’t recover within a few minutes or goes down, call your veterinarian. 

7. Photosensitization

Description: Although it’s commonly confused with sunburn or scratches. photo-sensitization is potentially much more serious. Primary photosensitization occurs when a horse eats a plant that contains a photodynamic compound that reacts to ultraviolet (UV) rays. When these compounds circulate in the blood system near the surface of unpigmented skin, the resulting chemical reaction damages tissues. In secondary photosensitization, a horse’s damaged liver cannot break down normal levels of photodynamic compounds, leading to the same reaction.

How you’ll recognize it:Photosensitization causes very painful blistering of the skin, followed by the formation of tight, crusty scabs. These will appear on pink skin under white markings and will slough off over time.

What you can do:Start by protecting your horse from sunlight. If his entire body is affected, have him spend his days in a darkened stall, shed or even an indoor arena. If the blistering is limited to his limbs, you can use standing wraps to shield them. If his face or muzzle are affected, use a UV-blocking fly mask with a nose flap.

Do not pick at the scabs, because this will be extremely painful for the horse and is unnecessary for healing. Let them slough off naturally. If the scabbing is extensive or your horse seems otherwise ill, call your veterinarian, who may prescribe anti-inflammatory medications or steroids for the pain.

Once your horse is tended to, spend some time determining why the reaction is occurring, if possible; check his pasture for plants that cause photosensitivity, such as alsike clover (Trifolium hybridum), buckwheat (Fagopyrum esculentum) or St. John’s wort (Hypericum perforatum). Also, ask your veterinarian to check your horse’s liver function. 

8. Sunburn

Description: Just as in fair-skinned people, sunburn in horses is the burning of the skin due to overexposure to UV radiation. Dark skin is protected by the pigment melanin, and your horse’s hair coat offers some protection as well, but pink skin with little or no hair covering—like on the muzzle—is more susceptible.

How you’ll recognize it:Sunburnt skin in horses is red, tender and swollen. In extreme cases, the skin may crack, bleed or ooze a bit of fluid. Extensive, tight and painful scabbing of the skin is more likely to be caused by photosensitization, which is a different pathological process and requires different treatment measures.

What you can do:Shield vulnerable areas of skin from sunlight. You can do this with sun-blocking gear—many fly masks incorporate nose flaps to cover pink muzzles—or with a thick coating of zinc oxide ointment. If your horse has sunburn, treat it tenderly with a thick emollient cream. If the sunburn doesn’t improve significantly within a few days, call your veterinarian.

This article first appeared in EQUUS issue #430.

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