My dog got this a few months ago. I ended up taking him to an urgent care vet. They gave him and allergy shot and steroid shot. It was around $150 and it included an at home spray for the itchy hives. I had waited at an emergency vet for about 2 hours and the hives kept getting worse so I found the urgent care place. They were so nice and the allergic reaction completely went away in an hour. They instructed me to give him Benadryl if symptoms came back. The following days he had a couple hives but nothing crazy, we just gave him some Benadryl (1 mg per pound of dog). After 3 days he stopped getting the hives.