Possible misdiagnosis for hairloss and scabbing?

I noticed a bald spot on the back of my cat's neck aprox. three weeks ago on a saturday, about the size of a dime. I went to the vet the following monday, and by then it had yellow scabs and was slightly larger. The vet took skin and hair samples and cultures, and looked under a microscope for mites. He said no mites were present, and gave me an all-around topical medication. Since then the lesion has grown to aprox. six inches in diameter, and has bled, peeled, and changed color. I have taken the cat back three times, and been given two different topical medications, oral antibiotics, cortizone shot, a biopsy, and on the most recent visit, an ivermectin injection (which I have since heard is not approved for use in cats, and the vet did not get my permission before giving the injection). I have not yet received biopsy results, but could it have been notoedric mites the whole time? The cat seems a little better the past two days as far as the lesion goes, but is not acting normal by any means(listless and uninterested in any activities though he still eats and drinks) could he be having a reaction to the ivermectin? Are vets required to get permision befor giving that sort of injection? so far we have spent upwards of $250 and my husband is upset at the vet, since the vet said the culture only grow a fungus that was not ringworm. Any advice would be greatly appreciated. Sorry the post is so long, thanks in advance. Mishon

Well, first I would find another vet. Vets tend to use the ivermectin quite a bit. They can give your can anything they want short of killing them. Theres not much you can do there. This may not be the answer, but we just had a cat at our clinic who had the same symtoms and it was actually worse and she was scabbed on the ears, nose and throughout the body. It seems this cat has a serious food allergy. Which could explain the symptoms and it may not be a reaction to the ivermectin at all. You may want to look for a vet who is VERY familiar with dermatology.

I am pretty sure it is not a food allergy considering my cat is very picky. He eats science diet dry food, and typically does not like kitty treats, soft food, or any other things other cats usually like to get into.

I have never had a problem with him garbage digging, and all of my plants or inaccessable to him. I will look for a vet familiar with dermatology though, thanks.

Oh no, it has nothing to do with xtras,treats or garbage. It can be a premium food or a crummy food. It does not matter. There may be something in there, even after eating the food for years that they develope a sensitivity to. It could be as simple as yeast,chicken etc. Like I said and you said you would look into a vet that is familiar with dermatology, its the first step in helping him.

Is your cat an indoor only? The reason I ask is we have a cat who was bitten by a spider, snake or something else that caused a reaction like you have described. We never did find out what had bitten her. Just doctored her and she eventually healed. Vet wanted to put her down, we refused and doctored her ourselves. She is now 4 years old. Beautiful little thing. Also had another cat who was allergic to grass pollen and fleas. Broke out everywhere. Had to put on allergy meds and keep her inside.

the cat is indoor only, never goes outside, and I have never seen a spider or any other bug in the house larger than an ant. I don't know what else it could be, considering all the tests keep coming up negative.