He doesn't get fleas much as he is mainly an inside cat (by choice) but he went for a walk and when we de-flea'ed him he still 'chased' the fleas around his back/leg/tail & chewed himself. So we re-de-flea'ed again 2 weeks later with a different potion
But he has developed a bald patch by his ear
So what do I do?
He is still chasing the flea around his back legs/tail
Sounds like he could have a flea allergy. Girl cat has one and its awful for her - you need to treat with a flea medicine that contains fipronil and wash all the bedding/soft furnishings if that's the case.