Allergic rhinitis occurs in response to triggers such as dust, pollen, mold and dander. If you have allergic rhinitis, your immune system produces a chemical known as histamine, which causes symptoms such as itchy, teary rhinitis, runny nose, sneezing, stuffy nose and coughing. Your doctor may prescribe corticosteroid and antihistamine medications to manage allergic rhinitis, after diagnosing the condition with a skin test or nasal and blood smear.
Nasal Smears
Nasal smears are commonly recommended to confirm allergic rhinitis. Your doctor or nurse may ask you to blow into a piece of wax paper to collect mucus that is spread thinly on glass slides. In very young patients, who cannot blow properly, a cotton swab is inserted into the nasal passage as far up as possible and rolled against the septum. The swab then is rolled on a glass slide to make a thin smear. The samples are sent to a laboratory, where technicians stain it with dyes and observe it under a microscope.
Nasal Cytology
Almost 60 percent of children with symptoms of allergic rhinitis contain increased concentration of eosinophils in the nasal secretion smears, according to a study published in the November 2006 issue of the journal “Pediatric Allergy and Immunology.” Eosinophils are white blood cells responsible for protecting the body against parasitic infections. They also play a key role in allergies and asthma. Another study in the February 1998 issue of the journal “Annals of Allergy, Asthma and Immunology” reaffirms that increased eosinophil count in nasal smears is a quick, simple and inexpensive tool to diagnose allergic rhinitis.
Results
The type and concentration of cells in a nasal smear also helps your doctor differentiate between different types of rhinitis. So, while the patients with typical allergic rhinitis have increased eosinophil count in nasal cytology, no such markers are found in the nasal smears of patients with vasomotor rhinitis, according to an article in the May 2006 issue of the journal “American Family Physician.”
Precautions
A study in the January 2005 issue of the “Indian Journal of Otolaryngology and Head & Neck Surgery” points out that the nasal cytology test for allergic rhinitis has moderately high sensitivity and high specificity. This means that the test can diagnose even small changes in the nasal mucosa and can effectively diagnose allergic rhinitis. However, as with any laboratory test, it is important to avoid contamination and mixing of samples. The smears should be made carefully without disrupting the cells. Make sure you follow all the instructions of your doctor carefully.
References
- Pediatric Allergy and Immunology; Prevalence of Allergic Rhinitis and Nasal Smear Eosinophilia in 11- to 15-year-old Children in Shiraz; S. Miri et al.; November 2006
- Annals of Allergy, Asthma and Immunology; Nasal Cytology in the Diagnosis of Allergic Rhinitis in Children; Orathai Jirapongsananuruk et al.; February 1998
- American Family Physician; Diagnosing Rhinitis: Allergic vs. Nonallergic; David M. Quillen, et al.; May 2006
- Indian Journal of Otolaryngology and Head & Neck Surgery; Diagnostic Significance of Nasal Eosinophilia in Allergic Rhinitis; Abhey Sood et al.; January 2005
