Skin problems - over grooming and scabs

Hi there We have a one year old rescue cat. We had him in December - no known medical needs - however in April he started getting small patches of no fur which would then turn into a raw sore (quite quickly). He also licks and bites a lot. The vets prescribed steroid injections, then steroid tablets - this has helped a little. He went off his food a lot in the last few months but is eating again now. He is still licking and biting a lot of the time and his fur, especially head, neck and legs, is quite thin. In the photo below, you can see a small white patch - the sore was also a small white patch until today. He goes outside when he wants, we live in an urban area but a relatively quiet one, with a few other cats. The vet felt it was some sort of dermatitis. Any other thoughts? We have insurance - the medication they are suggesting is around £120 a month, but I worry long term steroids are not good for him.

Hello!   "Dermatitis" is a description of a symptom, translating 'inflammation of the skin.'  If the skin is inflamed, then you have dermatitis.  The question is, what is causing it (it is very rare to know the answer on first presentation of the skin case).  When the cause is known, the best way to treat a lesion can be thereby be pinpointed.  Possibilities may include insect bites (there are preventative measures that can be taken) or allergies, including mites, flies or flea allergies (even in cases where there are no visible fleas - often the flea has long left the area before this kind of lesion is noticed by the owner.  Indeed, it is possible to be allergic to fragments of other cats' dead fleas).  Inflammation in general can be treated with anti-inflammatories but injectable steroids are very potent anti-inflammatories; so potent in fact, that they can affect the cat inside as well as out.  Because I don't know any more about this case than you have explained, I do not currently know why injectable steroids were chosen rather than, for example, steroid cream or even non-steroidal cream, or antibacterial / yeast shampoos, which act on the outside of the patient only.  It sounds as though good questions for your vet would include, why systemic steroids were appropriate and what long-term side effects they might expect to see.  Furthermore, what might be causing the lesions, how the possibilities might be narrowed down to find a preventative treatment or diagnosis and whether alternative ways of treating the lesions exist.