At a morning feed our 13 yr old gelding didn't come into the barn. We found him walking painfully slow to come in. He had strange, random swellings on his abdomen and chest, hard muscles, and one back swollen leg. The vet gave him 2 antihistamine shots that day and ongoing Bute, Banamine, and Tucomprim. The next 3 days he was better each day but the 4th day he was hardly walking again with some new swellings and now all 4 legs swollen. We think it is an allergic reaction but can't find any bite marks or sores and nothing had been changed that day before in his feed or pasture.
One week before we got a new load of coastal hay but we have 2 horses and the other, older one has no problems.
We rode in a field the night before and this horse was sluggish but beyond that was fine.
We are stumped as to what this could be. Any clues from anyone would be much appreciated. There are two photos from that first day - one of some swellings on one side and the other of the misshapen and swollen chest area.
Thanks for any clues you may have,