My dog has flea allergy... Shame I just can't afford flea stuff right now.

But anyway, I guess the bites are a whole lot worse to a dog allergic to the bites. My dog used to have patches of fur missing on his back and stuff before I changed his diet to a high quality food.. Now he still scratches and bashes himself against walls violently, trying to scratch.. But at least his fur is healthy.
Dog allergy is no fun. I think the trick is to try and keep their mind off it. He will sit there scratching literally all day, and chewing himself up, if you let him!
As for worse reactions, I am not sure really. I would be suprised if all dogs AREN'T allergic to fleas...