Allergists diagnose allergies by performing a physical exam and studying the patient’s medical history. They may also ask the patient to keep a diary of foods they eat and/or keep track of other things that might be causing allergies, such as exposure to pollen or cat dander. Allergists will also look for other potential causes for the symptoms experienced by the patient and perform a differential diagnosis.
The allergist might also perform tests to identify which allergens cause a reaction in the patient:
- Skin test: this test involves pricking the skin with a small needle that contains a tiny amount of a potential allergen. If the patient develops a hive or red bump at the injection site, that indicates an allergic reaction to the allergen used in the test.
- Radioallergosorbent test (RAST): this test involves examining the blood to determine whether IgE is present in the bloodstream.