Egg allergy anyone?

So my baby woke up on Thursday night all swollen up on his lip and privates area huge hives and swollen lip I rushed him to the ER not knowing what had caused it the Dr said it looked like a reaction to something he possibly ate. My son has never been allergic to anything. We we were told to keep a journal of foods he ate and how he reacted to them. Friday he was normal and saturday right after breakfast his hand started swelling. So after putting one and two together I noticed he had a homemade french toast saturday and on Thursday he had eggs for breakfast. Could it possibly be an egg allergy? What's weird is he's had eggs many times before he isn't a fan of them always but never had a reaction to then before

This is one pic of his swollen lip. His little privates were baaaaad it was scary.