We wormed our horses as usual but this time switched up the wormers and went with Eqvalan. One of our horses walked away, after worming, with his muzzle to the ground. This was unusual for him. We noticed he wasn't eating his hay though he was acting hungry. He did eat some pelleted feed. We checked him a short while later and the inside of his mouth, on both sides by the crease, were swollen. It appeared as if there were large absesses there. His mouth was very tender and he couldn't be held. Several hours later he was back to eating his hay with gusto but the same areas still appear inflamed but not swollen.
Has anyone else had a similar reaction to this wormer? Our other two horses appear fine. Thanks for any input. The Vet is coming out in the morning.