Pruritus (Itchiness) in Cats
Dr. Mark Thompson
Diagnosis A complete medical history. A thorough medical history is the foundation for the diagnosis of any dermatologic condition. The breed of your cat, the age, onset of symptoms, duration of symptoms, severity, season in which the problem occurs and the response to previous medications all are important clues.
The key to treating pruritus is to identify and treat the underlying cause. Your veterinarian may want to perform a few diagnostic tests to determine the cause of the pruritus. Tests may include:
A thorough physical examination. A complete general and skin examination that includes the skin, ears, footpads and claws is equally important. Unlike most organ systems in the body, the skin can be directly observed. Therefore, what your veterinarian sees is of value in establishing a diagnosis. Your veterinarian will usually look for primary lesions (those caused directly by the disease) and secondary lesions (those caused by your cat's response to the disease). The distribution of the lesions on your cat's body is critical to diagnosis since animals tend to scratch in certain areas with certain diseases. Also, a flea comb is often used to look for fleas, flea dirt or other parasites.
Skin scrapings. Skin scrapings are commonly done to diagnose skin parasites. A scalpel blade is used to scrape layers of skin that are then be examined under the microscope for mange mites and other parasites.
Fungal cultures. Your veterinarian may do a culture of the hair to rule out dermatophytes (ringworm). Although not always pruritic, ringworm can sometimes cause animals to scratch and can mimic other skin diseases. A small amount of hair is plucked from a skin lesion, placed on the growth media and incubated for 10 days to four weeks to observe for growth.
Blood and allergy tests. Your veterinarian may elect to do blood tests to assess other organs that may have an effect on the skin, or allergy tests or food trails if allergy is suspected.
The only way to relieve pruritus long-term is to diagnose and treat the underlying cause. Medications may be effective in mild cases or may offer temporary relief for more severe cases while waiting for the underlying cause to respond to treatment. But the itching often recurs after the medication is finished. Generally, treatment consists of the following:
Antihistamines. These drugs are much less helpful in cats than they are in humans and will significantly help only 25 to 30 percent of cases. Nevertheless, they are often prescribed since they are relatively safe drugs when compared to corticosteroids. Some cats respond better to one antihistamine than another, so veterinarians may try two or three different types before giving up on them.
Fatty acid supplements. These may help relieve pruritus by modulating the immune response and may be helpful for chronic pruritus. Certain fatty acids, such as eicosapentanoic acid found in fish oils, help to change the chemical composition of mediators produced during the allergic response, thereby making them less inflammatory. Like antihistamines, these products are not always helpful but they are relatively safe. Some cats that do not respond to antihistamines may do well with a combination of antihistamines and fatty acids.
Shampoo therapy. Shampoos that contain colloidal oatmeal are soothing, and because these shampoos are moisturizing, they can be used frequently without drying the skin. Some oatmeal-based shampoos contain topical anesthetics or topical corticosteroids that are safe and further help in reducing pruritus.
Corticosteroids. When other therapies are not effective, corticosteroids such as prednisone may be prescribed. Again, these drugs may help in some cases but are less effective in others. Many side effects associated with corticosteroids restrict their long-term use. Some of these include increased thirst and hunger, which may lead to obesity and suppression of the immune system, which may lead to infections, irritation of the stomach and damage to the liver or adrenal glands. Short-acting, oral corticosteroids are much safer than long-acting injectable, since they can be cleared from the body rapidly should side effects occur.