Hives during dinner

For dinner, Owen ate beef, rice with coconut milk, green beans and carrots. Owen started with beef and I saw some minor redness around his lips. It wasn't until he started eating the other food that the hives developed, and it was itchy. I gave him benadryl and it cleared up immediately.

I am concerned that he may be allergic to beef. But he ate beef during lunch which did not effect him and beef hot dogs never bother him.