my cat is 19; my vet says all OK, however he is showing some kidney malfunction, but due to his age, it is to be expected. the cat drinks a lot of water, but has a good appetite. he has had a nasal discharge for over 6 months; been on two antibiotics and a culture taken - nothing helps. His skin is crusty almost all over, and has lost lots of hair. vet gave me a prescription shampoo, but this has not helped. the nasal discharge is not as bad as it had been, but his skin is awful. I use Revolution per vet's recommendation and this keep's fleas off. any suggestions please on what can be causing this skin condition?

