Allergic rhinitis is an inflammatory condition of the nasal mucosa usually elicited by IgE-mediated response to allergen exposure. It is currently considered the most common allergic disease. Epidemiological research conducted in Poland between 2006 and 2008 identified allergic rhinitis in 23.6% of children aged 6–7 years, 24.6% of children aged 13–14 years and 21% of adults aged 20–44 years. It has been suggested by many authors that the inflammatory process in allergic rhinitis patients involves both, upper and lower respiratory tract. The aim of the study was to demonstrate the presence of lower respiratory tract inflammation based on fractional exhaled nitric oxide measurement. A total of 60 children were included in a 3-year follow-up study between 2011 and 2014 in the Department of Paediatrics, Paediatric Nephrology and Allergology at the Military Institute of Medicine, and the Outpatient Allergy Clinic. The study group of allergic rhinitis patients included 37 children (17 girls and 20 boys aged 6–18 years, mean age 10.4 years), while the reference group included 23 children (11 girls and 12 boys aged 6–12 years, mean age 10.8 years). Fractional exhaled nitric oxide levels were normal in most patients. No statistically significant differences in fractional exhaled nitric oxide were found between the study group (group I) and the reference group (group II), which would indicate the absence of inflammatory processes in the lower airways in the observed children.