Equine Skin Bumps May Be Eosinophilic Granuloma

Your horse has developed several firm bumps or nodules on his neck and back. Each one is about a quarter-inch to a half-inch across. There’s no sign of a cut or injury, they don’t seem to hurt or itch, and the hair covering them is in good shape. What’s going on?

There are several possible explanations for the skin bumps, one of which is the formation of eosinophilic granulomas. This type of bump typically follows a small scratch, insect bite, or even a routine injection that is administered with a silicone-coated needle. The minor irritation triggers a hyperallergic reaction, breaking down collagen in the skin’s connective tissues and attempting to isolate the injury by walling it off.

While the nodules are unsightly, they pose no threat to the horse unless they are in a place that may be abraded by tack. For nodules in an early stage, corticosteroid injections can shrink the bumps but probably will not entirely get rid of them. Older bumps that have calcified can be removed surgically.

If your horse’s granulomas have been caused by a reaction to insect bites, you can use fly spray and turnout sheets to minimize irritation from biting flies. However, the small bumps may just be something that your horse will develop from time to time, regardless of whatever you do to prevent them.

A veterinarian should examine skin bumps so a diagnosis can be made and treatment can be started.