Thanks for your replies everyone.

I was (and am still) beating myself over the the head for giving him the fish in the first place, but as you've all said, better to learn his allergies now, when he's with me than with someone who isn't watching him like a hawk.

Quote Originally Posted by mrspunkysmom
did you cook or spice the catfish in anything unusual?
No, just fish seasoning.

I hadn't heard of general seafood allergies, either. Just shell fish, but as others have said, I guess you can be allergic to anything. And luckilly, so far, he hasn't shown any other signs of other food allergies like eggs or peanuts.