Diagnosis

Your doctor will diagnose nonallergic rhinitis based on your symptoms and by ruling out other causes, especially allergies. Your doctor will perform a physical exam and ask questions about your symptoms.

He or she might recommend certain tests, although there are no definite tests for nonallergic rhinitis. Your doctor is likely to decide that you have nonallergic rhinitis if you have nasal congestion, a runny nose or postnasal drip and tests for other conditions don't reveal an underlying cause such as allergies or a sinus problem.

In some cases, your doctor might have you try a medication and see whether your symptoms improve.

Ruling out an allergic cause

In many cases, rhinitis is caused by an allergic reaction. The only way to be sure rhinitis isn't caused by allergies is through allergy testing, which may involve skin or blood tests.

• Skin test. To find out whether your symptoms might be caused by a certain allergen, your skin is pricked and exposed to small amounts of common airborne allergens, such as dust mites, mold, pollen, and cat and dog dander. If you're allergic to a particular allergen, you'll likely develop a raised bump (hive) at the test location on your skin. If you're not allergic to any of the substances, your skin will look normal.
• Blood test. A blood test can measure your immune system's response to common allergens by measuring the amount of certain antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies. A blood sample is sent to a medical lab, where it can be tested for evidence of sensitivity to specific allergens.

In some cases, rhinitis may be caused by both allergic and nonallergic triggers.

Ruling out sinus problems

Your doctor will want to be sure your symptoms aren't caused by a sinus problem related to a deviated septum or nasal polyps. If your doctor suspects a sinus problem, you might need an imaging test to view your sinuses.

• Nasal endoscopy. This test involves looking at the inside of your nasal passages with a thin, fiber-optic viewing instrument called an endoscope. Your doctor will pass the fiber-optic endoscope through your nostrils to examine your nasal passages and sinuses.
• CT scan. This procedure is a computerized X-ray technique that produces images of your sinuses that are more detailed than those produced by conventional X-ray exams.