title: Mycobacterium tuberculosis infection may protect against allergy in a tuberculosis endemic area.
abstract: BACKGROUND
  Epidemiological studies have shown an inverse relation of mycobacterial infection and the frequency of allergic diseases and asthma. Recent evidence suggests that allergic inflammation may be inhibited in the presence of chronic and persistent infections, such as that by Mycobacterium tuberculosis (MTB). The relation of tuberculin skin test (TST) size, an accepted marker of MTB infection and the frequency of allergic disease symptoms has not been reported from an area where MTB infection is endemic.
  
  
  OBJECTIVE
  To investigate the association of TST and allergic disease symptoms, in children living in a tuberculosis (TB) endemic area.
  
  
  METHODS
  In this cross-sectional study, 841 children aged 6-14 years from randomly selected household addresses in two poor communities of Cape Town, South Africa, were investigated with TST and standardized International Study on Asthma and Allergies in Childhood-based questionnaire on allergic disease symptoms.
  
  
  RESULTS
  Children with positive TST (> or =10 mm) were significantly less likely to have allergic disease symptoms, in particular allergic rhinitis (AR) (adjusted odds ratio 0.43; 95% confidence interval 0.24-0.79) than those with negative TST. This association remained significant after adjusting for possible confounders and correcting for the effect of clustering (>1 child per household address) in the sample. There was a significant inverse linear trend in the relation of TST size in millimetre and the frequency of allergic disease symptoms, in particular AR (P<0.001).
  
  
  CONCLUSIONS
  These results of inverse association of strong TST reaction and allergic disease symptoms in children from a TB endemic area are in support of the hypotheses that allergic inflammation may be inhibited by chronic infections, such as MTB.
authors.affiliation: Wilhelmina Children's Hospital, University Medical Center, Utrecht, The Netherlands. c.c.obihara@umcutrecht.nl
authors.forename: C C
authors.initials: CC
authors.lastname: Obihara
authors.forename: J L L
authors.initials: JL
authors.lastname: Kimpen
authors.forename: R P
authors.initials: RP
authors.lastname: Gie
authors.forename: S W
authors.initials: SW
authors.lastname: Lill
authors.forename: M O
authors.initials: MO
authors.lastname: Hoekstra
authors.forename: B J
authors.initials: BJ
authors.lastname: Marais
authors.forename: H S
authors.initials: HS
authors.lastname: Schaaf
authors.forename: K
authors.initials: K
authors.lastname: Lawrence
authors.forename: P C
authors.initials: PC
authors.lastname: Potter
authors.forename: E D
authors.initials: ED
authors.lastname: Bateman
authors.forename: C J
authors.initials: CJ
authors.lastname: Lombard
authors.forename: N
authors.initials: N
authors.lastname: Beyers
mesh_terms: D000293:Adolescent; D001500:BCG Vaccine / Q000008:administration & dosage; D002648:Child; D004196:Disease Outbreaks; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000382:microbiology* / Q000517:prevention & control; D008297:Male; D009169:Mycobacterium tuberculosis; D015995:Prevalence; D012044:Regression Analysis; D013019:South Africa; D014374:Tuberculin Test; D014376:Tuberculosis / Q000150:complications* / Q000517:prevention & control
chemical_list: D001500:BCG Vaccine