Warm temperatures and long hours of daylight bring greater opportunity to ride and enjoy your horse. But time spent outdoors during the summer can have downsides, too. What season-related health problems is your horse likely to encounter? Here are four common concerns to keep on your radar, plus ways to safeguard your horse.

1. Dehydration

In cool weather, an average 1,100-pound horse at rest drinks six to 10 gallons of fresh water a day. Summertime temperatures can boost daily consumption to 15 gallons. That amount may increase to as much as 30 gallons for a horse in exercise, depending on the temperature, humidity and his level of exertion. A horse working hard in the heat can lose two to four gallons of sweat per hour. Even so, he may not show signs of dehydration until he’s lost as much as 5 percent of his body weight in fluids. That’s 55 pounds for a 1,100-pound horse.

Dehydration can cause serious health problems, such as colic. At the extreme, it can be fatal. Signs of dehydration include:

• dullness
• lethargy
• loss of appetite
• red, dry mucous membranes inside the nose and mouth
• dry, sunken-looking eyes
• poor skin elasticity, indicated by a pinch of skin at the point of the shoulder remaining tented for longer than two seconds.

To keep your horse sufficiently hydrated, provide unlimited access to clean, cool water (ideally 45 to 65 degrees Fahrenheit). If he shows signs of dehydration, encourage him to drink at 10-minute intervals until he’s had his fill. To ensure that his water is fresh and palatable:

• empty and rinse water buckets daily
• clean outdoor tanks and troughs weekly to remove debris and algae
• check automatic watering systems daily to confirm they are delivering adequate amounts.

2. Anhidrosis

Even when the weather is hot and humid, some horses produce a reduced or inadequate amount of sweat. This can cause their body temperature to rise well above normal—to 105 degrees Fahrenheit and higher—putting these “non-sweaters” at risk of hyperthermia. A horse with anhidrosis may show these signs:

• a dry coat after work in warm weather
• decreased ability to perform
• increased respiratory rate
• increased rectal temperature.

Treatment may include medication, electrolyte supplementation and acupuncture. Most important: Ride your horse during the coolest part of the day.

3. Sunburn

Overexposure to ultraviolet rays can cause a familiar problem: sunburn. Melanin, a dark pigment contained in skin and hair, provides horses with some natural protection. But the lighter the color of the coat and the pinker the skin beneath it, the greater the risk of sunburn. You’ll recognize the signs, especially on white facial markings, muzzles, ears and legs: red skin that may blister or peel and is sensitive to touch.

To protect your horse from sunburn:

• Turn him out where he has access to shade, whether from a run-in shed or stand of trees. Place feed, water or a salt block in the area to entice him to spend time there.
• Schedule his turnout for the early morning or evening to avoid the hours between 10 a.m. and 4 p.m., when the sun is strongest.
• Apply a sunblock or sunscreen to vulnerable areas of skin. (Take care around the eyes.) Choose a product specifically designed for horses or use one made for people with sensitive skin. Some formulations for horses contain ingredients to repel insects and condition the coat as well. A thick layer of zinc-oxide ointment is a reliable barrier against UV rays. It also can help heal skin irritation and blistering. Whatever option you choose, apply according to label directions.
• Outfit your horse in wearable protection: a sun-blocking sheet, hood, mask (some have a nose flap for extra coverage) or leg wraps.

If your attempts at prevention fail, treat a sunburned horse’s skin as you would your own: Keep the area clean, apply a soothing ointment, such as aloe, and guard against further sun exposure. Hydration helps heal damaged skin, so make sure your horse has access to plenty of fresh, clean water. Call your veterinarian if the condition is severe or doesn’t resolve.

4. Bugs

Flies and other insects can drive your horse to distraction during the summer. Worse, they’re responsible for a variety of ailments. Whether through bites or their attraction to body secretions and open lesions, summertime pests can

• transmit disease, for example Potomac horse fever from caddisfly and equine infectious anemia from horseflies.
• trigger allergic reactions that show up on skin, such as blackfly dermatitis, horn fly irritation and sweet itch from the Culicoides midge (no-see-um).
• deposit infectious organisms where they feed. For instance, the worms that cause summer sores (habronemiasis) and the fungi responsible for rainrot (rain scald) are carried by both stable flies and houseflies attracted to moisture and wounds on skin.
• cause your horse to hurt himself. If he’s bothered enough by flying pests, he may bruise a hoof from stomping or self-inflict injury as he tosses his head or otherwise fidgets in his stall as he attempts to evade them.

To safeguard your horse against summertime insects:

• stable during the times that bugs are most active, generally during the day
• position fans in the stable so the airflow makes it difficult for insects to land on your horse
• apply long-lasting repellents, available in several varieties, ranging from sprays and wipes to roll-ons and ointments
• outfit your horse with a lightweight fly sheet, mask and boots.

Sound management practices, too, will reduce the number of pests you and your horse have to contend with. An effective strategy includes:

• managing manure to break the insect life cycle. Regularly collect it from the barn and paddocks. Then compost it, spread it or have it removed.
• eliminating breeding sites: areas that are wet, muddy, swampy or have rotting vegetation
• installing fly traps and tapes
• using fly predators, tiny insects that naturally control flies by feeding on them before they can mature.

Practical Horseman thanks Laura Hutton, MVB, of Palm Beach Equine Clinic in Wellington, Florida, for her technical assistance in the preparation of this article. A lifelong equestrian, Dr. Hutton is a graduate of the University College Dublin School of Veterinary Medicine in Ireland. She joined Palm Beach Equine Clinic in 2016 and focuses primarily on emergency and sports medicine.

This article originally appeared in the Summer 2021 issue of Practical Horseman.