A Case of Hives Horrifies Horse Owner, but the Common Ailment Is Easy to Treat

I remember the first time Cricket got hives. I had never had a horse or seen a horse with hives and it was quite a sight to see.

I went down to the barn for the morning feed and there stood my beautiful horse with lumps all over the sides of her neck. I called a friend and asked if she’d come take a look and after describing what I was seeing. She said simply, “Oh that’s just hives, don’t worry about it.”

Don’t worry? My horse had lumps on both sides of her neck about the size of a decent heel blister after wearing the wrong shoes, but there weren’t that many so I took her advice and remained calm. Off to work I went and I thought about my poor baby all day. Upon arriving home and going to the barn for the evening feed the lumps were joined by bumps (larger lumps) and were more numerous and had spread down her neck to her shoulders and were beginning to appear on her sides.

I called my more experienced horse friend again and she said, with a small giggle, “Huh, just give her Benadryl. Break a few tablets open and add it to her food, hives are no big deal in horses.”

I have to say that I was beginning to worry and thought I’d better look into hives—what they were and how they were caused. Besides, there was no way I was giving my precious horse a medication I wasn’t sure was safe to give her. I hit the veterinary care book I had in my barn first aid box to look up hives and found that they are a symptom of an allergic reaction to something such as bug bites, food allergies and a host of other causes.

Thoughts ran through my head, questions really: What had caused my horse to have hives? She’d been out grazing all day just like every day. I hadn’t given her anything different to eat at all. Hmmm? Maybe something bit her.”

I decided not to give her the Benadryl since the book said hives weren’t dangerous, merely a symptom, so I had to find out what had caused this reaction in Cricket.

At the following morning feed Cricket, was covered in lumps and bumps and those on her sides had become larger and raised to nearly the size of the tea cup saucers I have in my kitchen. It looked almost like ringworm to me (that’s a whole other topic to cover) and through her hair I couldn’t see if there was any sign of fungus. The center of each saucer was flat and jiggly with a raised circular edge. I freaked out and called the vet to come out right away. He asked during our brief conversation if she had any other symptoms, like shortness of breath, and I was thankfully able to say no. He said he’d be out within two hours. Two of the longest hours I’d ever lived.

When the vet showed up he examined Cricket and said she was fine but had a pretty fair case of hives. He asked if she had eaten anything out of the ordinary and I said not that I was aware of. He asked if she’d been out grazing and I told him she had just like every day. He said that there was most likely something growing or blooming that she hadn’t had exposure to and was exhibiting a reaction to it.

He told me that different plants grow and bloom at different times of the year and that I should probably keep her in her corral or pasture so she can’t get into whatever it is, since we have no way of knowing exactly what the cause is. It made sense to me since I hadn’t had her very long at that time and this was her first spring season with me. He gave me some steroidal medication to give her for five days that smelled and looked like powdered sugar, but it really did the trick. Within one dose she was markedly improved and was completely clear by the end of the course of the meds.

During my research on hives I found out that hives are variable‐sized patches of edema (swelling) that can occur anywhere on the body, especially on the neck, sides of the body and upper areas of the limbs, which is what I saw initially in Cricket. They may or may not be itchy and cause discomfort to the horse.

I didn’t ride during her bout with hives as they ended up in her girth area too and I didn’t want to cinch the saddle on in case there was pain. Hives are apparently pretty common in horses, which was news to me, and the cause is often difficult to determine. They can be caused by hypersensitivity or allergic reactions, insect bites and stings, physical forces like sunlight, extreme temperatures, exercise, physiologic stresses, genetic abnormalities, drugs and chemicals, infections, plants and food, to name a few. The most commonly reported causes of hives in horses are drugs such as antibiotics and food, and can even be secondary to infections or parasite infestations. 

Later that same year we were well into summer and Jane was in foal and she and Cricket were out grazing again. I had purchased a mare-and-foal feed for Jane to keep her in tip-top condition during her pregnancy and I kept it in the barn in a can with a tight lid. Low and behold I came home from work one day and found Cricket in the barn, can of mare-and-foal feed spread all over the floor, and she had eaten so much of it her midsection was as hard as a basketball.

Of course I had to call the vet for advice, since she had eaten pounds and ponds of the feed all at once. He advised that I not feed her that evening or the next morning and keep an eye on her. Guess what happened? Hives! Thankfully that was her only reaction and at least this time I knew what they were and the cause.

I called the vet out and another course of steroidal meds cleared the problem. I was relieved there was no colic or other more threatening reaction to her macking down all that rich feed. I locked up the barn and put the mares in the pasture so Cricket wouldn’t get into any more trouble, at least for awhile.

I never gave her Benadryl and never will. I like to play it safe when it comes to a very important part of my family. Hives no longer scare me or worry me much, but I will always call the vet if they ever appear again in my pasture.