She may have food allergies. Food allergies, in cats, shows up as skin lesions. Food allergies can develop over time. To determine if she has food allergies, she would need to be put on a completely hypo-allergenic diet for 6 weeks. The name of the diet is called "hills z/d." You have to get it from a veterinarian. There are no over the counter diets that will work for the food allergy test.
She could also have environmental, or inhalant allergies, which is called "atopic dermatitis." Your vet could do a blood test to see what she is allergic to. Then you could try and avoid what she is allergic to. She could also receive "allergy shots" to desensitize her to the allergens. Allergy shots are 50-70% effective in pets.
The other option is to treat her symptomatically. You can use antihistamines, steroids, immune suppressing allergy treatments, and topical treatment.
You can try giving her an antihistamines. For cats, we usually start with chlorpheniramine. It comes in 4 mg tablet. You would need to give 1/4 tablet every 12 hours for allergies. You can buy it at a drug store.
You can also use hydrocortisone spray. It helps with inflammation. Apply it to the affected area 3-4 times a day until it looks normal. It is not toxic if she licks it. You can also try the hydrocortisone cream but that is more messy.
You can also add an omega-3 fatty acid supplement to her diet. The omega-3 helps with skin inflammation and skin allergies. They have commercially available preparation such as "3V liquid." You can buy it online or at a pet store. You can also try fish oil. Give 1/8 teaspoon of the fish oil for the first week. If she does not have loose stool, gradually go up to 1/2 teaspoon twice a day.
Even if she indoors there is still a possibility that she has a flea saliva allergy. If this is the case, one flea bite will cause her to have a big allergic reaction. You can buy a cheap plastic flea comb at the pet store. Brush down her back, about 10 times. Take all the hair, and everything else, and put it on a white paper towel. Add a few drops of water. If any of the black specs turn rust color, that is digested blood from fleas. You can buy advantage drops, over the counter, to treat for fleas.
Metabolic disease, such as hyperthyroidism and kidney disease, are both common in cats as they get older. Both cause vomiting. So it is highly possible that she has metabolic disease. A blood test would rule that out. If she has kidney disease she would be put on a special diet, stomach acid reducers, fluid therapy, and medication to reduce the work load on the kidneys. If she has hyperthyroidism, from a benign tumor on the thyroid gland, she could take a daily medication to bring her thyroid levels back to normal.She could also have inflammatory bowel disease. This is where the immune system goes out of control and causes inflammation in the intestines. We usually treat it with anti-inflammatory medication and if it responds well, then it is inflammatory bowel disease. But the only true was to diagnose it is to take a biopsy of the intestines.Canned food is easier to digest than dry food. I would switch her over to canned food, over a weeks time, if she is not already on it. Add a little canned food to her dry food each day. If she completely refuses to eat canned food, you can add broth, or water, to her dry food. But canned food works better. You can also give her a human stomach acid reducer. 1/4 of a 10 mg pepcid tablet, 2-3 times a day, works well. If she is not already on hairball prevention, that can help too. Petromalt, or laxatone, paste 2-3 times a week is good. But they have found that chronic hairball vomiting is due to an underlying condition and not the hairballs themselves. I hope this helps.If you have additional questions, please click reply.
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I JUST WANTED TO LET YOU KNOW THAT SHE IS NO LONGER SHEDDING AND MY SUSPICIONS WERE RIGHT. ABOUT A YEAR AGO I ASKED THE HABDYMAN TO PUT A NEW TRAY UNDER THE TOILET TANK .HE IS HARD OF HEARING AND JUST TIGHTENED THE OLD ONE UPMEVEN THOUGH I WAS STANDING THEREWITH A NEW ONE.SO I LAID IT ON THE FLOOR IN HOPES HE WOULD COME.I ALSO LAID THE ALUMINUM HOLDERS ON THE FLOOR.ONE DAY I WAS IN THERE AND NOTICED SHE WAS CHEWING ON IT. WHEN I TOOK IT AWAY THERE WAS ABOUT 6 INCHES MISSING. SO I TOOK IT AWAY. NOW SHE NO LONGER SHEDS BUT I AM STILL GIVING HER HAIRBALL FOOD TOO.I THOUGHT YOU MIGHT GET A KICK OUT OF IT.