Consider possible causes

Hives are an immune response to a topical or systemic allergen. Investigate whether something in your horse’s environment may have led to the reaction. The first exposure to a new allergen won’t trigger a reaction, but the second or even third might. Consider any recent management changes you may have made.

• Have you started using a new fly spray?

• Is the horse on a new medication?

• Has he been moved to a different pasture?

• Is he being fed a new grain or hay?

Look for other clues as well. If the hives are limited to the saddle area, for instance, the trigger may be the detergent used to wash the saddle pad. Jot down your ideas to share with the veterinarian when she arrives.

If wheals appear on only a small area of skin, douse them with cool water.