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Allergic Rhinitis (Hay Fever): Diagnosis

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This information was reviewed and approved by Rafeul Alam, MD, PhD (2/29/2020).

Often a person has more than one type of rhinitis at the same time.

In making the diagnosis, the evaluation by your doctor may include:

  • History: The doctor will ask questions about your health and your symptoms.

  • Physical exam: The doctor will complete a physical exam along with other tests.

  • Nasal smears: Nasal secretions are examined under a microscope.

  • Allergy skin testing: Skin testing by a board-certified allergist is often recommended for someone with recurrent symptoms. A skin test detects the presence of antibodies to a particular allergen, a substance that causes an allergic reaction. A positive test suggests that you may have an allergy to the particular substance. A skin test is performed by first placing a drop of allergen extract on the skin, then the skin is pricked. If you have a positive reaction to the extract, a red welt will appear on your skin in about 15 minutes. The size of the welt may indicate the strength of the reaction. If you do not react to the extract, you are most likely not allergic to the substance. In most cases, an allergic person will react to more than one substance. Your doctor will compare your prick skin test results with your history of symptoms to confirm which allergens are causing your symptoms.

  • Sinus CT scan: Changes in the sinus CT scan may indicate sinusitis (inflammation of the sinuses) with or without sinus infection or nasal polyps.


Hay Fever Diagnosis FAQs

Question: How can I tell whether I have allergies or just a cold?

Answer: Generally, allergies last longer than a cold, often for a few weeks. If you notice a pattern in which you suffer the same symptoms at the same time year after year, you are likely suffering from allergies. Frequent sneezing and itchy, watery eyes are more often associated with an allergy, rather than a cold. Also, a clear nasal discharge suggests that you are suffering from allergies. When you have a cold, the mucus is usually greenish or yellowish. A low-grade fever may also indicate a cold. Sometimes it can be hard to tell the difference between seasonal allergies, a cold or another condition. That's when skin tests and an evaluation by an allergist may be necessary.


Question: I am 68 and seem to be developing allergies to flowers, tree pollen, etc. How do I find out what I'm allergic to, and do I need to start year-round treatment?

Answer: The best way to diagnose allergy is skin testing and evaluation and interpretation of your history and skin test results. It would be unusual for someone age 68 to develop new allergies, but it is not unheard of. We recommend an evaluation with skin testing by an allergist.


Question: How can you tell the difference between an allergy and exposure to mold?

Answer: To differentiate mold allergies from other types of allergies, an evaluation by an allergist — including skin testing — would be required. The exact role of all molds in causing sinus and lung disease is very complicated and the focus of a lot of research.


Question: What is the difference between RAST testing and skin testing? Is one more beneficial than the other?

Answer: RAST testing is a term that is often used to describe blood test for allergy (although most currently used blood tests for allergy are no longer truly a RAST test), while skin testing involves plastic needles that are used to prick the skin of the patient. RAST testing is sometimes a reasonable alternative when a patient cannot stop antihistamines. RAST stands for ‘radioallergosorbent test’ and measures the amount of IgE antibody in the blood — the antibody involved in allergies. Due to improved laboratory techniques, the radioallergosorbent test is no longer performed. The newer laboratory techniques more accurately measure allergy antibody levels than the old RAST testing.

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