Cats can suffer from allergies, producing a range of symptoms, including itchy skin (and redness if the cat has been persistently scratching itself), sneezing, asthmatic wheezing, vomiting, diarrhea, and bloating.
Allergies occur when the immune system overreacts to a foreign substance, usually harmless, leading to the release of an inflammatory chemical such as histamine in the body.
Common triggers include: fleabites; food—usually proteins in meats such as beef, pork, or chicken; airborne particles such as pollen; and contact with a substance such as wool or detergent.
The surefire way to treat an allergy is to remove the trigger, but it may be difficult to find the exact cause. A vet may prescribe antihistamines, which relieve itchy skin. Pest control is necessary if fleabites are the cause.
Autoimmune disorders are caused by an overactive immune system, which attacks the body’s own tissues. Although rare in cats, they include a group of skin diseases known as pemphigus complex and the multisystem disorder systemic lupus erythematosus (SLE).
The immune system may also be underactive or weakened with age. Certain feline infections attack cells of the immune system, making the cat vulnerable to other infections and cancer.
Such pathogens include the feline immunodeficiency virus (FIV), which attacks certain T-cells, and feline leukemia virus (FeLV), which may cause cancer of white blood cells.