Summertime brings eager mosquitoes and gnats that "bug" (get it?) all humans and equines, but some horses are a little more affected than others. This equine had welts from his stomach all the way to his ears, and everywhere in between. Some horses just have extreme sensitivities to those mosquitoes and gnats.
It's tough to see here, but you may notice that this welt covered horse is spared on his hind end. Typically, you'll see that even those most sensitive horses don't have welts on their hindquarters. Why is that? Their tail, of course. A horse's tail is designed to keep irritating bugs from biting, and they are great at their job (if not wrapped).
How can you help protect the rest of your horse? There are a few strategies. You can, of course, keep them inside at dawn and dusk (prime insect feeding time) until October. We realize that this is unrealistic for many, but there you have it. Fly sheets can be used as a physical barrier from bugs, and are effective. Fly sprays have varying effectiveness, but are worth a try. And finally, for extreme cases, antihistamines and steroids can be prescribed by your veterinarian to reduce your equine's reaction.