Urticaria (Hives)

This 6 year old thoroughbred gelding presented with a sudden onset of severe urticaria caused by an allergic reaction.  Urticaria is sometimes known by its more common name of "hives".  This poor fellow was literally covered head to hoof with large skin wheals and was feeling pretty off colour and lethargic as you would expect.  Urticaria can be caused by any number of allergens, the most common in horses are insect bites, drug reactions and contact allergies (plants/shampoo etc).

This gelding had been in the same stable for some time, had not been washed or treated with any medications recently and had been fed the same diet for several weeks.  With this history it is quite likely that he had been stung by an insect such as a bee or wasp and that was what had caused the severe reaction that you can see in the photos.  He was treated with intravenous injections of cortisone and anti-histamine by on of our vets and made a fairly rapid and uneventful recovery over the next 6-8 hours.

Allergic reactions of this type are usually quite mild and can vary from a light skin rash to severe urticaria such as in this case, but they can on occasion be be very serious.  Often horses may appear dull and lethargic but sometimes can be quite aggitated as the hives can be very itchy and irritating.  Cold hosing may temporarily alleviate the irritation caused by the skin wheals but veterinary treatment is usually warranted especially if the horse is uncomfortable. 

An anaphylactic reaction is a severe multi-systemic allergic reaction which is life threatening even if treated immediately.  The most common cause of anaphylaxis in horses is a reaction to improperly administered drugs, so be very careful when you are giving injections to your horse and always ensure that you follow the dose and administration directions from your vet carefully.  Always talk to a vet before treating an animal yourself.  If you think your horse is having an allergic reaction call your vet as soon as possible.