Diagnosis of allergic asthma begins with a trip to the physician. The physician will review the patient’s medical history, ask questions and conduct a physical examination including listening to the chest with a stethoscope. The physician may also recommend a chest x-ray to check for lung disease or pneumonia, a sinus x-ray and a sputum culture, which is a test that checks for the presence of bacteria in coughed-up mucus.

Additional tests may be performed to identify other potential causes for allergic asthma symptoms. A pulmonary function test (PFT) may be necessary. The PFT is a painless and noninvasive test that measures lung function. A PFT involves the patient exhaling into a spirometer, a device that measures the volume of air in the lungs and determines how quickly the patient can get air out of the lungs. The PFT results will indicate to the physician the patient’s lung function.

Allergy skin tests may be performed to identify specific substances to which the patient is allergic. Skin testing is fast and simple and involves introducing a small amount of allergen to the skin to provoke a reaction. A positive test for an allergen occurs when the skin reddens and swells. 

Blood tests may be performed to determine the amount of a particular substance in the blood and identify abnormally high or low levels. Blood tests will involve drawing blood from the patient and sending the blood to a laboratory for analysis. Blood tests may cause discomfort but are generally not painful.

Difficulty in diagnoses or in treatment may require the physician to perform thorough tests that examine the specific structure of the nose and upper and lower airways of the respiratory system. The following diagnostic tests may be performed in some cases of allergic asthma:

• Anterior rhinoscopy. This procedure allows the physician to examine the inside of the nose. This will help the physician determine whether the symptoms are caused by nasal abnormalities like polyps. The procedure will cause no discomfort.
  
  
• Nasal endoscopy. A special telescope is inserted into the nose and/or sinus cavities to allow the physician to examine those areas. It can be used for both diagnosis and as a guide during surgical procedures.
  
  
• Computed axial tomography (CAT) scan. This test will show cross-sectional images of the inside of the head. The test will allow the physician a three dimensional view of the sinus cavities and determine the healthiness of the sinuses. The patient may be required not to eat or drink before the test. The test will take 15 to 30 minutes to perform and does not cause discomfort.