Does your horse have allergies?


So this is a giant can-o-worms. A horse that has allergies can give you all sorts of confusing signs, and there is not really a simple test you can do. Time to play detective with your vet.


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Horses, like all creatures, can be allergic to things.


  • When a substance (AKA allergen) like mold or dust or bug comes into contact with your horse, the immune system kicks in.


  • Antibodies are made to fight the allergen present in your horse.


  • When you have an allergic reaction, there is a hypersensitivity to these allergens and the immune system goes into over-reaction mode. You could say your horse’s immune system goes a bit bonkers.



horse with large bug bits on her side

HIVES. And really big ones, at that!


How does an allergy manifest itself in your horse?


  • Typically, there are a few ways. We are probably all familiar with hives, which usually occur around the neck and shoulders. Skin allergies are often revealed to us with the raised, and usually itchy as heck, bumps we call hives.


  • Some horses are so itchy that they will rub and scratch and roll until they are missing hair and damaging skin. Hives can also be a problem if they are so far-reaching that they impair the breathing ability of your horse. It’s always best to call a Veterinarian if your horse has hives. Just in case.


  • We can also witness a respiratory allergy reaction. It’s widely believed that heaves are some sort of allergy.


You may also notice that your horse has trouble with forming proper manure, in which case diarrhea could be warning you of an allergic reaction.


  • Just a quick note about diarrhea – this is never something to watch and wait to see if it clears up. It can be life-threatening, contagious, and warrants a call to your veterinarian immediately. Diarrhea has a long list of possible causes, allergies being only one of them.


vet truck


There are a zillion things that could trigger allergies in horses:


  • Dust


  • Mold


  • Proteins



  • Flies


  • Hay


  • Pollen


  • Ingredients in food


  • Topical products we use


allergy testing results

What allergy blood testing results look like.


How to test for allergies.


  • There are skin hypersensitivity tests that inject tiny amounts of isolated allergens into your horse’s skin. There are also blood tests for allergies.


  • This is much discussion and research as to the efficacy of these tests. I’ll tell you from personal experience that the blood allergy test was a huge benefit when I was faced with possible food allergies in a horse. This made doing the elimination test much easier.


Elimination tests for horse allergies


  • The best way to test for allergies is to perform elimination tests, in which case you must alter the environment and strip the diet down to the most basic elements to see if eliminating a substance allows your horse to return to normal.


  • This is easy to do if you suspect an allergy to something, perhaps a grooming product you have. Just stop using it!


  • For suspected food allergies, you must strip the diet to the minimum and add single ingredients back in. This takes time, of course! Your veterinarian and equine nutritionist will be able to help you plan this out over several weeks or longer.


hors supplements being put into tub

When performing elimination tests, add one ingredient back in at a time.


  • You should also know that allergies can suddenly appear, so even if you have been feeding XYZ for eons, one day your horse may develop an allergy to it. The same goes for things in the air, like pollen, and even for grooming sprays we like to use.


If you suspect allergies or have a case of hives, respiratory issues or digestive issues, it’s worth investigating with your veterinarian.


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