Kelly!! I haven't seen a cat allergy like that, I do know that you can get hive type symptoms from some dogs, like Shar Pei's tend to give me the hives if I have to restrain them for work... but cat allergies tend to be more hay fever like symptoms.

I hope it isn't Simba. Maybe try giving him a bath?? (how funny would that be....) see if that helps. Just a warm salt water bath should help pull away any stuff on his fur like dander or something that can help.