It happened again last night. Are ants really the problem? Did he do it again??

Smokey and I were on the couch and P.C. was being whiney, I thought it was just cuz he couldn't fit up there with us.
So I got up and played with them and things were fine. Then he was whiney again even though I made room for him on the couch.
So I said, OK, we'll all go lay in my bed, ya big baby.

We went upstairs and we all layed down but he was still whiney. So I took a closer look and noticed he was starting to look bumpy again and there were small welts appearing on the underneath part of his hind legs.
I called my roommate and told her; she asked me to give him some Benedryl and she was on her way home.

I didn't see him this morning, but I know he was hurtin' and swelling up last night.
I gave the dogs eggs w/ their dinner on Tuesday (the first time it happened) and yesterday but Smokey is OK and P.C. didn't start to welt up until 4-5 hours later. What I've read about food allergies is that the reaction will occur within about 20 minutes so I don't think it's the eggs (plus, he had one w/ dinner over the weekend and was fine).

SO... I'll see how he is today... And if my roommate is planning on taking him to the vet or what. Poor fella.