Cat allergies can be diagnosed through a combination of medical history, physical examination, and various diagnostic tests. The following are the most common ways to diagnose cat allergies:

1. Medical History: The first step in diagnosing a cat allergy is to take a thorough medical history. Your doctor will ask about your symptoms, when they started, and how often they occur. They may also ask about your exposure to cats, such as whether you have a pet cat, live with someone who does, or have had close contact with cats at work or school.
2. Physical Examination: Your doctor will perform a physical examination to check for any signs of allergy, such as skin rashes, hives, or red and itchy eyes.
3. Skin Prick Test: A skin prick test is a common diagnostic tool for cat allergies. In this test, a small amount of cat allergen extract is placed on the skin, and then the skin is lightly pricked. If you’re allergic to cats, you’ll develop a raised bump or redness at the site of the prick within 15 minutes.
4. Blood Test: A blood test, also known as a radioallergosorbent test (RAST), can also be used to diagnose cat allergies. This test measures the amount of specific antibodies in your blood that are produced in response to an allergen.
5. Challenge Test: A challenge test, also known as an inhalation challenge, is another option for diagnosing cat allergies. During this test, you inhale cat allergen under controlled conditions in a medical setting. If you have a reaction, such as wheezing, coughing, or shortness of breath, it suggests that you’re allergic to cats.
6. Patch Test: A patch test can be used to diagnose contact dermatitis, which is an allergy that occurs when the skin comes into direct contact with an allergen. During this test, a small amount of cat allergen is placed on a patch that’s applied to your skin. If you’re allergic to cats, you’ll develop a rash or redness at the site of the patch within 48 hours.

It’s important to note that no single test can confirm a cat allergy with 100% certainty. Your doctor may use several tests to get a more complete picture of your condition and determine the best course of treatment.

In conclusion, diagnosing cat allergies requires a combination of medical history, physical examination, and various diagnostic tests. Your doctor may use a combination of tests to determine the best course of treatment for your specific symptoms. If you suspect that you have a cat allergy, it’s important to seek the advice of a healthcare professional for an accurate diagnosis and appropriate treatment.