A. If the lesions clear up with a steroid shot, that would imply to me that this is a disease that has to do with the immune system. Steroids suppress the immune system, and prevent it from reacting. Typically in animals with auto-immune diseases the immune system is either reacting too forcefully to something that it should basically ignore (allergies) or attacking its own tissues for reasons we don't understand.
It's possible that your cat had fleas at one point and unfortunately now has an allergy to fleas. Cats with this problem will react significantly to even one flea bite, because of the allergy. So not only must the cat be continually protected against fleas (with a monthly product to repel them) we must also manage the allergic disease. This means immuno-suppression like she's already gotten in the form of a steroid shot. Under almost 99% of circumstances I don't recommend these long-acting steroid shots due to severe side effects with chronic use. There are many other safer alternatives in the form of oral medications that can be used.
She could also have allergies to something other than fleas - something in the environment or something in her food. It's worth trying a trial of a hypoallergenic food in order to see if the condition improves.
If a food trial fails, and if managing the disease as if she was allergic ultimately doesn't provide complete relief, then the area needs to by biopsied in order to obtain an exact diagnosis, and treat appropriately.
A. This type of skin rash is common with flea allergy dermatitis. The symptoms do usually subside temporarily with a steroid shot, but after the effects of the shot wear off (usually 4-6 weeks), the rash will return if the flea problem is not resolved. Sometimes it can be difficult to find fleas on your cat because they are constantly grooming themselves and will commonly lick and swallow the fleas. Your veterinarian can go through her coat with a fine toothed comb to look for flea "dirt", which is the waste that fleas pass. This is good evidence that your pet has fleas. Not all cats are allergic or hypersensitive to flea bites, but the ones that are characteristically get a bumpy, scabby skin rash above the tail and often around the neck. In order to avoid getting repeated steroid shots, discuss what is the best flea prevention for your cat with your veterinarian. You should treat all pets in your home, not just the one with the skin rash. Some commonly used and effective flea treatments for cats are Frontline Plus, Advantage, or Activyl.
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