A doctor diagnoses chronic, nonallergic rhinitis by considering a patient's symptoms and ruling out other possible causes, according to Mayo Clinic. Typical signs of chronic rhinitis are nasal congestion, runny nose and postnasal drip. Sinus troubles and some allergies also produce these symptoms, so tests are run to exclude those conditions.
It is possible for doctors to rule out deviated septum or nasal polyps as the cause of rhinitis through imaging tests, notes Mayo Clinic. Doctors insert fiber-optic nasal endoscopes into the nostrils to view nasal passages and sinuses. In addition, computerized tomography, or CT, scans create clear images of these areas. If nothing appears abnormal, theses possibilities are checked off the list.
Testing for allergies that cause rhinitis involves skin or blood tests. In a skin test, the skin is punctured several times, and small amounts of environmental allergens, such as dust mites, mold and pollen, are introduced, explains Mayo Clinic. If a hive develops, the patient is allergic. A lack of skin reaction indicates no allergy is present.
Doctors also perform blood tests to look for certain antibodies that the immune system creates in response to allergens. If the antibodies are not present it the blood, the patient has no allergies. When sinus conditions and allergies have been eliminated, chronic rhinitis is most likely the cause of the symptoms, according to Mayo Clinic.