What these three scenarios have in common is that they may be indications that your horse is having an allergic reaction to, or experiencing a side effect from, something he ingested, was injected with, or came in contact with. Like people, horses can experience allergic reactions or side effects from a wide variety of substances or drug combinations, some quite serious.

“Allergic reactions can present with a myriad of different signs – anything from a welt at an injection site, hives or heaves, to full-blown anaphylactic shock,” says Dr. Bri Henderson, equine veterinarian and instructor in the University of Guelph’s on-line equine course programs. “Because of the potential severity of an allergic reaction, they are always in the back of my mind when I administer a drug. However, I would thankfully not classify them as a common occurrence.”

History and Interactions

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