Itchy skin from flea meds?

I have a large, male Maine coon with a food allergy on a grain free diet that has always had dry skin. In the winter the cool air humidifier runs 24/7. A few weeks ago, I found a flea on him after a trip to the vet. They gave me Para Defense, a new generic med. Two weeks later and I can't find a flea on him but it had dried out his skin! The last five days he has been taking omega 3 vitamins with his wet food but will NOT STOP biting his paws!!! He's no longer ripping out fur, behavior, bathroom and eating habits are all normal, just the constant paw biting! Any suggestions on how to get him to stop? Anyone else experience flea meds drying out the cats skin?

Is it only his paws he's chewing?  This seems like an odd thing for a flea med to cause?  I'd be looking at something else I think.  Have you contacted your Vet and explained what is happening?  I'd definitely mention it and see what they think might be going on.  

For the dryness, perhaps try rubbing a little oil on them.  Olive oil, coconut oil,

Called the vet today, they've never heard of flea meds causing it. Said to stick with the omega 3 vitamins. The water where I live has reeked of chlorine lately, googled it and that could intensify his already dry skin! Bought spring water for him, hopefully this will do the trick!!