A friend of the family went on a trip with us over the weekend. Yesterday his horse, Toby, broke out in what looked to me like hives, as if he was having an allergic reaction, but he didn't have any fly spray or anything on him. Just his tack. It started about 2 hours into the ride. He told me that it happens all the time when he rides, But this time has been the worst. He thinks it may have something to do with his nerves, since he is a stallion and is pritty hyper. Any ideas on what it could be? He wanted me to take these pics so he could show his vet.
Left hind quarter... this is where it was the worst
He had a few bumps on his neck and chest too, but it wasn't anything like his back legs and rump.
He didn't seem to act like it botherd him, and wasn't sensitive to touch