Hope your boy is doing better. I'd sure watch his breathing through the night and be sure the swelling is going down. I had one swell up at a show - actually two different times at the same show barn - the second time he swelled from nose to tail, his ears were even swollen and his breathing was restricted. We got Dexamethasone and benedryl into him, ran cold water on him (it was summer). I've never seen a horse so swollen, and we never knew for sure whether it was the shavings, a spider bite, or most likely, some very strong liniment I used on him. The good news is that he recovered and has not had another episode. Hoping the best for your guy.
Jan