@amdeemer My Martha loved to chase bugs. Last summer a wasp stung her in the mouth. She swelled up her eyes swelled shut, and she got hives all over. I just happened to have prednisone here, from another incident. I gave her a prednisone and two benedryl. She weighed about 45 lbs. It took awhile-several hours, but her swelling went down, and little by little the hives started to go away-she was covered in hives. As long as his breathing is not affected, keep any eye on him, and give him another benedryl. If I were you, if he does okay, I would keep some pred.(ask your vet) on hand, in case next time is worse. Hope he will be okay.