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Help! My Horse Has Horrible Hives!

Dear Dr. Gray, my 10 year old quarter horse developed hives about the size of a half dollar to a quarter ALL over his body. He has never had hives before. The other five horses on the farm do not have hives. My vet put him on HistAll antihistamine at that time. They went away in a week and then came back in two weeks. I continued him on HistAll with minimal affect. My vet pulled blood and sent it away to a lab in Arizona. The allergy test came back that he is allergic to 17 things ranging from wool, at the top of the list, to willow trees. We sprayed the field he is kept in for weeds and molds, which were six of the allergies. We changed his hay to fescue because he is allergic to timothy, johnson, and orchard grass. I have taken away all the possible things showing up on his allergy list. However, we cannot keep him safe from the pollens and molds on the allergy list due to the weather and wind. We have had him on flax seed meal, Spirolina, and BioZin with his grain and antihistamine with direction from my vet.

The hives went away again in mid June for a week and then returned. My vet gave my horse a shot of Dexamethasone and capsules if needed. The hives went away immediately, but returned five days later. I started him on the capsules. The hives went away after two days. I stopped the capsules as told by my vet. Five days later the hives started to return; I repeated the two days of capsules; hives gone. I am waiting for the next five days to see what happens. The hives return smaller and fewer each time. My vet suggests I start him on desensitizing shots prepared by the lab that tested him. He says this process only has a 60% cure rate, but I should try. Is there another process or professional I can try? We live in Virginia where it has been unusually hot and dry. Many people are having hive trouble, but not this severe. We moved here just before this, so I guess it is the region. HELP! I would appreciate your opinions and suggestion. – Thanks, SS

Dear SS,

Of all the skin conditions horses get, hives has to be one of the most difficult ones to deal with. You almost need to be Sherlock Holmes to figure out what causes it! On top of that, the medication regimen can be expensive and complicated and doesn’t always work or keep working. And your poor horse looks and feels miserable. You didn’t mention if yours was itchy as well as lumpy, but many are.

I like that you’re on products with omega-3 fatty acids, as research has shown they help maintain healthy skin and even support healing of certain skin conditions, like hives. I would also place MSM in this category. Another ingredient many horse owners have great success with is adaptogens such as the herbs found in APF. Until you can discover and remove the stimulus though, antihistamines and steroids will also be necessary. You may want to ask your veterinarian if a different kind of antihistamine or steroid might work better in your individual horse.

Since your horse never had hives before you moved to this new area, it does sound like something in the new environment is causing this reaction. The choices are many: something in his diet, something he’s inhaling, something he’s coming in contact with, etc. His hives could also be caused by a hypersensitivity to insects.

You can either systematically eliminate potential causes one by one and wait to see if he gets better or you can attempt to diagnose the cause by testing. Unfortunately, testing is controversial, as some feel the blood test your veterinarian has performed is not as useful as intradermal skin testing. Before you start the desensitizing injections based on results of the blood test, talk to your veterinarian about the pros and cons of intradermal skin testing. Or, ask him to help you get a second opinion at the nearest referral center, whether a private practice or University.

In the meantime, keep your horse as comfortable as possible. Give frequent cool baths—with or without a soothing shampoo or other product—and protect him from insects with a fan in his stall and a mask, sheet and leggings during the day.




Lydia F. Gray, DVM, MA SmartPak Staff Veterinarian and Medical Director Dr. Lydia Gray has earned a Bachelor of Science in agriculture, a Doctor of Veterinary Medicine (DVM), and a Master of Arts focusing on interpersonal and organizational communication. After “retiring” from private practice, she put her experience and education to work as the American Association of Equine Practitioner’s first-ever Director of Owner Education. Dr. Gray continues to provide health and nutrition information to horse owners through her position at SmartPak, through publication in more than a dozen general and trade publications, and through presentations around the country. She is the very proud owner of a Trakehner named Newman that she actively competes with in dressage and combined driving. In addition to memberships in the USDF and USEF, Dr. Gray is also a member of the Illinois Dressage and Combined Training Association (IDCTA). She is a USDF “L” Program Graduate and is currently working on her Bronze Medal. Find Dr. Gray on Google+

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17 comments on “Help! My Horse Has Horrible Hives!
  1. Cindy LeGrand says:

    I,too, have a qtr horse that gets big-wheeled hives seasonally. He is allergic to gnats, that thrive in wet climate. Like clockwork, when it rains, the gnats hatch and he breaks out. I have had some success with vinegar, both as an oral treatment, and sprayed on as a ‘bug spray’. I feed apple cider vinegar, 2 cups per day. Then use clear vinegar mixed 2/3 vinegar with 1/3 water as a bug spray. I spray on morning and evenings, when gnats are most active. Be careful tho’, vinegar can sting in open wounds and eyes. It’s inexpensive by the case, and moderately effective.

    • Butch says:

      I just went through a very bad session of Hives all over my Rocky Mountain horse. He had oozing sappy sores all over his face and Huge Hives all over his body. I spent days researching and not calling vet since I did not want to give him steroids. I wanted a natural way to rid this horrible set of Hives. I got Omega Horseshine (I had used before years ago love it) MSM, and COugh Free. I mixed all with some senior feed with a bit of water to make a doughey past so he would eat it all. AND IN 4 DAYS HE IS CLEAR! I am excited and Thankful for other remedies that are Natural! YEA!

  2. Christine says:

    This has to be a Virginia thing. Im having similar problems (though we arent this bad yet). Its so frustrating especially when out of 15 horses hes the only one.He gets hives, he molts entire areas of his coat. We go between medicating and bathing and blanketing and its just not a fun cycle.

  3. Jodi says:

    My daughter’s Arab gelding has had hives since he received a vaccination in April! We are losing our minds trying to treat. I have learned you must be super careful with using the Dex. Horses on Dex are more prone to Laminitis and, if your horse is prone to ulcers, the Dex can aggravate the ulcers (sadly, we learned the hard way). If ulcers are an issue, make sure you give omeprazole along with Dex.
    We have tried eliminating everything ( bedding, sheeting instead of fly spray, different hay, different barn) all to no avail. I was told not to waste money on the blood test but to do the intradermal. Of course, once allergens are identified, there is no guarantee they can be eliminated.
    I am open to any other suggestions, I am now soaking his hay (miserable in winter). Had ulcers when we got him (just over a year ago), hives began with vaccination and are only kept away with Dex.

  4. Sherry Stowman says:

    Antihistamines work well to relieve symptoms of different types of allergies, including seasonal (hay fever), indoor, and food allergies, but they can’t relieve every symptom. To treat nasal congestion, your doctor may recommend taking a decongestant. Some drugs combine an antihistamine and decongestant…^….

    Be well

  5. colette says:

    My 6 year old quarter horse mare developed hives this last summer. Nothing had changed for her environmentally. I had the intradermal skin testing done and am now giving her the desensitization shots. Her biggest reaction was to wool. Most of her hives were under the saddle pad. I had tried the the other treatments mentioned and they only worked short term. I chose to do the shots because I cannot possibly eliminate all her triggers. Since the shots began and I put a cotton pad next back, she has been hive free. I lost the whole training and show season last year. I was ready to try something because I was unable to ride her. The shots are expensive initially due to the frequency they had to be given. The cost will be substantially less when she gets them every 21 days. I have my horse back because of the shots.

  6. Susan says:

    We purchased a new horse 4 weeks ago. Within the first week with us, she broke out in hives…her whole body! She was so itchy. Gave her dex (powder) for 10 days to no avail. Stopped her itching a bit, but she still has them. Many oozed, scabbed and have fallen off. 2 weeks ago I noticed them on another horse, not as many and she didn’t seem to be affected by them. Now yesterday I noticed my 3rd mare has them! I am in southern Alberta and we have a new acreage. The later 2 horses have been there all summer. My guess is a seasonal plant that they are reacting to as it is dying or dead. My next step is trying to ID plants and contact someone to help us get rid of the unwanted vegetation.

  7. shellee says:

    I have a mare that is going through her second round of hives. They started when I got new grass hay, (at least I think). At the same time I got the hay, the flies and mosquitos were also starting to bite. So I believed the bumps were due to the bugs. In December I noticed the hives were huge and covered her neck and stomach. I took her to the vet, got her a steroid shot and three weeks of hydorx. steroid pills, (20 a day). After one week of finishing her meds, she is starting with new hives, though much smaller. I ordered new grass hay tonight, in hopes this will help her. I am so worried I won’t be able to get this under control.

  8. Twain says:

    I have been dealing with hives on my mare for two years. She is on allergy shots, hay cubes and dex. I can honestly say the only time she is hive free is when she is being ridden. this winter she has been off for three months. After about a month of being off, she started to break out. again this is the same pattern when being laid off. My belief is exercise keeps the lymphatic system etc flowing and releases the toxins, etc.

  9. BB says:

    I have a 10 year old gray QH show mare that his been retired from showing three months ago. She is now a broodmare. We pulled her shoes off and I started turning her out to pasture during the day. Over a month and a half ago she started getting hives. They looked so bad. Most of the hives were 2 to 3 inches across, and were circular. She looked like the surface of the moon. My breeding vet has been giving her a shot of antihistimine/steroids about once a week to help control it. After the shot, the next day the hives are gone. By the fourth day they are back. Since the first week the hives appeared, I’ve kept her off the grass in case there’s some type of weed(s) in the grass she’s having a reaction too. I’ve changed types of shavings for her (didn’t work). I’ve changed alfalfa (didn’t work). I’ve changed feed (didn’t work). I’ve put a lot of fly spray on her (didn’t work). I’ve tried no fly spray to see if she’s having a reaction to the fly spray (it didn’t work).

    This has been so puzzling and frustrating. My vet is cautious with the shots because my mare is 24 days pregnant. I’ve even asked him if she’s allergic to being pregnant. The only thing that has changed in her care since retiring her is she doesn’t get ridden 6 days a week (she’s not being ridden at all), and she’s not hosed off 6 days a week (after being ridden). Also, I’ve stopped giving her Platinum Performance CJ.

    I’ve consulted my other vet that I use, and he gave me a special soothing shampoo and lotion to try. I’ve done this twice, I could tell she loved the bath and the hives did diminish a little bit, but they kept coming back and getting larger and lumpier.

    As of now, I have her turned out in a covered round pen 24 hours a day to see if I remove her completely from the shavings helps.

    Maybe there’s some gnats that I can’t see that are bothering her? But you would think the fly spray would stop them. She’s not swishing very much at flies.

    My next step is to put her back on Platinum Performance CJ to see if there’s an ingredient in there that was keeping her from having hives. I’ve owned her since 2010, and I’ve never had an issue with hives before. I feel so sorry for her.

    Should I start riding her lightly again? I’d hate to overexert her while pregnant. I could ride her bareback with the hives so I don’t have to tighten a cinch around her girth area.

    • SmartPak SmartPak says:

      Hi BB, I’m sorry to hear about your mare’s hives, they can definitely be frustrating. What I love hearing is that you’re working closely with both of your veterinarians, as that is absolutely the most important considering her hives and her pregnancy. One point I noticed is that you recently took her off a formula that was providing omega 3 fatty acids, which can help to support healthy skin. It might be worth chatting with your veterinarian about the possibility of putting her back on a product with omega 3’s, or seeking additional diagnostic tests, perhaps from a specialist. This case may continue to be trial and error, and I wish you the best of luck in finding the solution! – Dr. Lydia Gray

  10. Tink Thran says:

    I have a 5 yr old qtr horse mare. She has recently brook out in hives. There is no change in feed EXCEPT.. she was started on her 7 day sand purge. She has been on it before and I didn’t notice any hives. I have seen in your posts omega-3 fatty acids, is that a supplement or by it’s self. I have her on a supplement that she has been on for over a yr, pretty sure it’s not that causing the hives. I feel bad for her because I don’t know what to do. Any help will be greatly appreciated…

  11. horse 1 says:

    My friend has a male horse with terrible hives. He is a horse that was brought to her because of his hives she has tried almost everything how can she get rid of them?

    • SmartPak SmartPak says:

      Thanks for your question. I’m sorry to hear about what your friend’s horse is going through. The most important thing for your friend to do will be to work closely with her veterinarian to try to determine the underlying cause and to come up with the best plan to support her horse going forward. This may include systematically eliminating causes and/or intradermal or blood tests to help determine what is leading to her horse’s reaction. Her vet may also suggest hyposensitization injections, and including nutrients like omega 3s and MSM in her horse’s diet, depending on the individual horse and situation. For more information on this topic, please see the blogs below.

      – Dr. Lydia Gray

  12. Janis says:

    Ahh. I’ve had my mare 6 yrs and now she is getting hives. We have had a lot of wet weather. Molds and pollens. This is the 4 th time time. She had a injection in the chest fall shots that’s the only diff. Thing that’s been done. Rabbis and Rhino shots.
    She is on dex. The other horses don’t have it.

  13. Leilah says:

    My horse develops hives every spring – and summer time. My vet and I know it’s not very serious, but while I do things around his stall I sometimes notice him itched them. They are located at the stifle on both sides of his butt. Any tips or things that may be able to help with the hives?

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