Determining the specific allergen that is causing an allergic reaction can be difficult. A physician will compile a medical history and a list of symptoms in trying to diagnose an animal allergy. A physical examination will also be performed. If an animal allergy is suspected, physicians may have patients fill out a questionnaire about their frequency of exposure to animals, symptoms and possible triggers.

A patient may be asked to avoid the animal for several weeks or longer, if possible, to see if allergy symptoms subside. However, this is usually considered to be unreliable because animal dander can persist in a home for months after an animal has been removed from the home.

There are two scientific methods used to determine animal allergies: through the skin and through the blood. Because the skin is the body’s most sensitive organ, it reacts quickly to allergens. Through skin testing, usually by a prick to the skin on the arm (allergy skin test), the physician can determine if the patient is allergic to animal dander.

If a skin test for dander is negative, the physician may test for other allergens such as saliva, urine and epithelium (a type of tissue). If the test results are inconclusive, the suspected allergen may be injected beneath the skin’s surface (intradermal test) to yield better results.

In some animal allergies, reactions take the form of a skin rash and are more difficult to diagnose. A blood test called a radioallergosorbent (RAST) test takes longer to yield results, but it may be able to definitively pinpoint the allergen causing a reaction.