Diagnosis

To determine the cause of allergic rhinitis, the doctor will ask a number of questions about:

• Time of day and year of rhinitis episodes. Rhinitis that appears seasonally is typically due to pollens and outdoor allergens. If symptoms occur throughout the year, the doctor will suspect perennial allergic or non-allergic rhinitis.
• Family history of allergies.
• History of medical problems.
• In women, if they are pregnant or taking drugs that contain estrogen (oral contraceptives, hormone replacement therapy).
• Use of other medications including decongestants, which can cause a rebound effect.
• Pets.
• Any additional unusual symptoms. As examples, bloody nasal discharge and obstruction in only one nasal passage could suggest a tumor. Fatigue, sensitivity to cold, weight gain, and depression may be signs of hypothyroidism.

Physical Examination

The doctor will examine the inside of the nose with an instrument called a speculum. This is a painless examination allowing the doctor to check for redness and other signs of inflammation. The doctor will also usually check the eyes, ears, and chest.

Allergy Skin Tests

A skin test is a simple method for detecting common allergens. Patients are usually tested for a panel of common allergens. Skin tests are rarely needed to diagnose mild seasonal allergic rhinitis, since the cause is usually obvious. The skin test is not appropriate for children younger than age 3.

• Patients should not take antihistamines for at least 12 - 72 hours before the test. Otherwise an allergic reaction may not show up.
• Small amounts of suspected allergens are applied to the skin with a needle prick or scratch or are injected a few cells deep into the skin. The injection test may be more sensitive than the standard prick test.
• If an allergy is present, a hive (a swollen reddened area) forms within about 20 minutes.

The test is not completely accurate. For instance, a 2001 study reported that testing detected allergies in less than half of children with rhinitis. Furthermore, about 15 - 20% of people may have a skin reaction without actually having an allergy.

Laboratory Tests

Nasal Smear. The doctor may take a nasal smear. The nasal secretion is examined microscopically for factors that might indicate a cause, such as increased numbers of white blood cells, indicating infection, or high counts of eosinophils. High eosinophil counts indicate an allergic condition, but low counts do not rule out allergic rhinitis.

Tests for IgE. Blood tests for IgE immunoglobulin production may also be performed. One test is called the radioallergosorbent Test (RAST), used to detect increased levels of allergen-specific IgE in response to particular allergens. Blood tests for IgE may be less accurate than skin tests. They should be performed only on patients who cannot undergo skin testing or when skin test results are uncertain.

Imaging Tests

In people with chronic rhinitis, the doctor may also check for sinusitis. Imaging tests may be useful if other tests are ambiguous.

• A test called transillumination, in which a doctor shines a bright light against the patient's cheek or forehead, is an inexpensive method for checking for abnormalities in the sinus cavities, although it is not highly accurate.
• CT scans may be useful for some cases of sinusitis.

Nasal Endoscopy

In certain cases of chronic or unresponsive seasonal rhinitis, a doctor may use endoscopy to examine for any irregularities in the nose structure. Endoscopy uses a tube inserted through the nose that contains a miniature camera to view the passageways.

Review Date: 12/21/2006
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.

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