Hi had same with one of my cats thought it was flea allergy. She was fullof flaes when we gother and although it was over 10 years ago I thought it looked the same
Took her to the vet who stated that if I was frontlining her as I 'claimed' she couldn't have fleas. No way could the Fleas develop an immunity. And I was. it got to a point, well I have 2 cats, she was always more of an indoor, back garden only if its dry and warm. He's a wander everywhere and anywhere type, but she was so stressed I actually thought about keeping him in incase he was bringing fleas hom,e even though he was fine.
Scrubbed/steamed etc the house from top to bottom, still she had bad skin and getting to the point of biting herself.
It got to a point, well I have 2 cats, she was always more of an indoor, back garden only if its dry and warm. He's a wander everywhere and anywhere type, but she was so stressed I actually thought about keeping him in incase he was bringing fleas home even though he was fine.
She was so unhappy, losing weight so stressed, we were back and forward to the vets, it was silly
Anyway a friend eventually said you know what what harm will using a different flea treatment do?
So I bought and used Advantage, and the change within 2 days was amazing.
She was back to her full coated/ sheding every where self within a month, though as I said in 2 days she was clearly happier and eating much better.
I know one story doesnt make data but its worth considering
even as just elimation of any other causes
I now have a supply of both Advantage and Frontline, so if the same starts to happen I can get in quick.
BTW we never saw fleas/ got bit/ other cat fine, she seems to one of thoes that the fleas like, in the way midges never bite me, but mozzies love me I am necter to them.