My general feeling is that the citrus allergy is likely real, if only because it limits the foods Rodney can eat, and I don't see him doing that for something that's not real.

The hypoglycemia, eh, I suspect he's a lot like me and gets icky when his blood sugar drops. I don't have any problems with fiction that treats it as real, but my general sense is that it's probably an exaggeration.

I don't actually see them treated all that derisively on the show, any more than Rodeny's tendency to talk about how brilliant he is.