Cat mystery hair loss

Hi my cat has (had) FIP and is currently being treated with GS and has 1 month of treatment remaining. She has had her neck shaved and blood tests a couple of times. She started with a small patch but 2 weeks later she is now progressively loosing fur on her neck above where she’s been shaved and itching. Stuck as to what this is! Vet doesn’t suspect ringworm, we have also checked under the woodlamp (not glowing) and I’ve been using canesten cream and it’s still spread like this. Now vet suspects dermatitis possibly caused by the numbing cream to her neck and has given me Fucicort cream to try. Please could I  have some insight? She’s been so ill and I’ve spent over £6000 on her GS medication and hospitalisation so far and I really can’t afford to keep going for tests at the vet. First pic is how it started second is it now. Thank you  

Hello - Some forms are hair-loss are to do with the quality of the hair / infections etc.  Common ones include Ringworm and Demodex, both of which are more likely when a cat is systemically ill eg with FIP, but neither of these would  typically present with rubbing or itching.  Your vet sounds to have started to rule Ringworm out, although not all cases of Ringworm show up with a Wood's Lamp.  (Demodex can be ruled out with skin-scrapes).    Alternatively, could this be an example of hair-loss secondary to rubbing or scratching by the cat? - in which case common culprits might be fleas, stress, toothache and pain.  Cats do not show pain as humans would expect and therefore it is frequently underdiagnosed.  Finally, there is the drug GS itself which does have some dermal side-effects, usually in association with vasculitis (inflammation of the veins) and usually associated with the extremitis.  I hear that you are having to use your vets a lot at the moment but please do make sure that they are aware of this worsening hair-loss so that they can take any steps that they need to.  Skin problems are rarely only skin deep.