Hives are very common events in horses. The problem is determining what the horse is reacting to as it can be just about anything the horse comes in contact with. This article covers the cause, diagnosis, and treatment of hives in horses.

Recognizable as an acute onset of multiple nodules or plagues in the skin. There may be only one or a few or the whole body covered. Frequently they are bilaterally symmetrical. The skin may be hot and the horse pruritic (itchy) but often there is no discomfort. The swellings are in the skin itself not under the skin. There is no hair loss, and if large enough they pit, like a firm sponge when finger pressure is put on them. When the finger is removed the impression remains for several seconds or longer then fills back in. Occasionally they become moist from serum weeping.