As long as the airways aren't being blocked by any swelling your can wait till the vet gets there. He will give him a shot and they should clear up pretty quick.
I had a horse get into a fire ant hill. She got bitten all over her face and neck.
I don't recall what the shot was but it was pretty fast working.
I like to keep antihystamine powder on hand in my vet kit for just such emergency's. You might ask your vet for some to have on hand. I think I pay around $17-$20 for a container.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France