Expert: Dr. Louis N. Gotthelf - 1/1/2006

Question
My 6 year old male cat has had a skin condition for about 8
months now. It is mostly on his lower back but will spread to
other parts of his body, paws, neck, face etc. without treatment.
It gets crusty and red underneath the crust/flakes. I have been
taking him to the vet on a monthly basis and they have been  
giving him cortizone shots, which seem to clear it up for about 3
weeks and then it's back again, and just gets worse if I don't
take him  in for another shot. Fleas, parasites, etc. have been
ruled out and I have also switched his food to Science Diet
Sensitive Skin, he does not eat any other food or treats, that
hasn't helped. The vet also shaved his back where most of the
irritation is found, that didn't help either. I have noticed that
where the fur is growing back extra thick, the irritation seems to
be much worse. It seems to be painful and itchy, he is an
overweight cat, so he can't really reach his lower back to clean it
or scratch it. It also makes him very grumpy. I really don't know
what else to do. Please help! Thank you.

Answer
This is probably an allergy and if the cortisone shots help, then the vet can "tweak" the treatment.  Some cats can take cortisone pills in addition to the shot.  Others require shots every 2 weeks until the skin is quiet and then they get a shot every 3-4 weeks.  Sometimes topical cortisone spray or ointment helps.  And some cats respond to an antihistamine called chlorpheniramine.

Other cats with skin disease are allergic to the food, but usually cats show itching on the face when they are food allergic. Some cats respond to the cortisone initially, but require antibiotics to treat the secondary bacterial infection that sometimes occurs when the skin is so irritated.

It is hard to determine the exact reason.  If you can bathe the cat, that helps remove surface allergens.  Some cats are allergic to fleas and it can take as few as one flea bite every 30-45 days to keep the flea allergy going.