When cats have itchy skin, they groom themselves more. Their little barbed tongues scratch the itch but also pull out or break the hair in the areas being licked. The result is a cat with areas of short hair or no hair. Common locations are the legs, belly and lower back. Although many times the owners don’t notice their cat grooming more (they tend to do this when alone or bored) this is almost the only way that a cat can have these areas of hair loss or shortened haircoat.
Occasionally, about 10% of the time, overgrooming is due to stress. The cat grooms itself more to relieve anxiety, just as a nervous person might chew his or her fingernails. The other 90% of the time, the cat is itchy due to allergies. It’s no fun to be itchy constantly, in fact it’s a pretty miserable way to live. Raw, irritated skin can also become infected and then we have two problems to treat instead of just the original one. If there is some mild hair loss but the skin itself looks normal a cat may need minimal treatment, but the worse the hair loss, the more itchy and uncomfortable the cat.
The question we usually ask when a cat is itchy is “Allergy to what?” One of the most common causes is a little mite called Cheyletiella. Most cats have at least a few of these microscopic mites living in their hair follicles with no ill effects. The problem develops when the cat becomes allergic to the mites. The allergic reaction leads to the itching and pulling hair out, not the mites themselves. Since there are often only a few mites causing the problem they can be very difficult to find. Instead of doing multiple skin scrapings to find mites under the microscope, we generally treat itchy cats for these mites and see if the itching subsides.
Other skin parasites that can cause itching in cats include Sarcoptic mites, Demodex mites, ear mites and fleas. We used to use Revolution topical ointment for all of these but it does not kill Demodex mites. Bravecto is a newer flea and tick control ointment. Bravecto only needs to be applied every 12 weeks, and it kills Demodex mites as well as the other types, so we are now using Bravecto more often than Revolution.
Demodex is more likely to cause skin lesions on the face, whereas flea allergy tends to cause more itching around the lower back and hind legs, so sometimes we have other clues to help us to determine our treatment plan. If fleas are suspected the home will need treatment as well as the pets. As with mites, if a pet is allergic to fleas they can be very itchy from just an occasional flea bite, so using flea preventive products is always a good idea for itchy cats.
If there are multiple pets living in the house, all of them need to be treated so the allergic cat doesn’t pick parasites back up again from another member of the household. Humans can be carriers of Sarcoptic mites, too, either with or without having itchy skin.
Allergy to pollens, molds, mildews and/or house dust mites is a common cause of itching. The same allergens that cause hay fever symptoms in people cause itchy skin in dogs and cats. This type of allergy is called atopy. When cats are allergic to pollens their itching and overgrooming is usually seasonal – they will be itchy during the time of year when the plant they are allergic to is pollinating. Molds, mildews and dust mites are present in the home all year ‘round, although warm, humid summer weather tends to make mold and mildew allergies worse and dry, dusty indoor air in the winter can worsen dust mite allergies.
Seasonal allergies are usually treated with steroids such as prednisolone, but we try to avoid keeping cats on this type of medication all the time, due to the risk of side effects.
Cats are very resistant to steroid side effects but by the time they’ve been taking these drugs for two or three years they will usually start to have problems, including weight gain, increased risk for diabetes, thin skin, liver swelling and increased urination. Using pred for a few months every year is fine, but using it constantly all year is not good.
Unfortunately, antihistamines don’t work real well for many allergic cats, plus they taste bitter and can be difficult to administer. Fatty acid supplements or a diet containing extra fatty acids can be helpful. Blood or skin testing can be done to determine exactly what the cat is allergic to, so the cat can be given allergen injections. There are also some newer medications we can try, such as Atopica, and special shampoos and sprays that may be helpful. Our goal is to keep the cat reasonably comfortable, though we often can’t eliminate the itching entirely without giving more steroid than is safe to use. Treating the itch is usually a process of trial and error to figure out what works the best for the particular cat.
Cats and dogs can also be allergic to food substances. About 15% of itchy cats are food allergic, and many have both atopy and food allergy. If treating for mites isn’t effective, and especially if the itching isn’t seasonal, it’s time for a hypoallergenic diet trial. (Please see separate handout on that.)
The fungal infection commonly known as ringworm can cause overgrooming. Ringworm is especially common in outdoor cats or ones with malnutrition or serious health problems that would lead to a compromised immune system. Ringworm is contagious to people as well as pets, so it’s important to rule this type of infection out.
Some cats with ringworm have the classic symptom of round, scaly, ring-shaped skin lesions on the legs and face, but ringworm can also cause classic allergy and overgrooming signs. We may need to do fungal testing to make our diagnosis. We have a new antigen test for ringworm that is much more accurate than culturing the fungus.
So where does all this information lead us? It’s basically working through the list of possibilities a few at a time. We usually start with Revolution/Bravecto and steroids, plus antibiotics if the skin is infected. If we are suspicious of ringworm we will send hair samples to the lab. Where we go from there depends on how the cat responds and what we find on our tests. Hopefully we can make the itchy, overgrooming cat feel better soon!
|Causes of Overgrooming||Diagnostic tests||Treatment|
|Cheyletiella mites||Treatment trial||Revolution/Bravecto|
|Demodex mites||Treatment trial||Bravecto|
|Sarcoptes mites||Treatment trial||Revolution/Bravecto|
|Fleas||Exam for fleas & droppings||Flea control for home & pets, Rev./Bravecto|
|Atopy||Steroid trial, allergy testing||Allergy medications|
|Food allergy||Hypoallergenic diet trial||Special diet|
|Ringworm||Fungal culture||Antifungal medication|
|Secondary bacterial infection||Skin scrape or exam of skin||Antibiotics|
|Stress||Antianxiety medication trial||Medical & behavioral therapy|