Inverse association between Mycobacterium tuberculosis infection and atopic rhinitis in children

Background: The association between Mycobacterium tuberculosis (MTB) infection and atopy remains controversial. Aim: To investigate the association between MTB infection and atopic rhinitis in children living in a high TB incidence area. Methods: In this cross-sectional study 418 children aged 6-14 years from an established epidemiological research-site in a poor urban community were invited to participate. They were assessed for allergic rhinitis (ISAAC questionnaire) and skin responses to tuberculin and eight environmental allergens. The presence of a BCG scar was documented, intestinal parasites and total and Ascaris lumbricoides-specific IgE levels were measured. Atopic rhinitis was defined, using the new World Allergy Organization (WAO) definition, as reported allergic rhinitis and a positive skin prick test (SPT >= 3 mm) to any allergen. Results: Among the 337 children enrolled 10.4% had allergic rhinitis, 17.5% a positive SPT and 53% a positive tuberculin skin test (TST >= 10 mm). Children with a positive TST were significantly less likely to have recent atopic rhinitis (ORadjusted 0.06; 95% CI 0.007-0.5) than those with a negative TST. SPTs were significantly more common in children with negative TST who had recent allergic rhinitis (ORadj 34.0; 95% CI 7.6-152.6), but not in children with positive TST and recent allergic rhinitis (ORadj 0.6; 95% CI 0.07-5.2). Conclusions: MTB infection seems to reduce the prevalence of atopic rhinitis, and influences SPT reactivity in children with allergic rhinitis from a high TB incidence area.