Childhood atopy and allergic disease and skin test responses to environmental mycobacteria in rural Crete: a cross-sectional survey.

Background: Through its powerful immunoregulatory effects, infection with atypical mycobacteria may exert a protective effect on the development of childhood allergic disease.

Objective: To examine the relationship between childhood atopy or allergic disease and previous infection with four species of atypical mycobacteria.

Methods: Eight hundred and six children aged 8-18 years and living in rural Crete--most of whom had had previous BCG immunization--underwent skin prick testing with 10 aeroallergens; their parents completed a standardized questionnaire relating to allergic disease. No less than 8 weeks later each child underwent intradermal skin tests with 0.1 mL solutions of four selected mycobacterial reagents (Aviumin C, Gordonin, Chelonin and Ranin I).

Results: Twenty-three percent of children were atopic on skin prick testing; far fewer had symptoms of asthma (5%) or hayfever in conjunction with a positive prick test to pollens (2%). Eighty percent of children had positive skin responses to one or more mycobacterial species. Among all children--and those with a BCG scar--there was no association between atopy or allergic symptoms and mycobacterial skin responses; among the few children without a BCG scar however those with positive mycobacterial responses were less likely to be atopic or to report allergic symptoms; these differences were not statistically significant.

Conclusions: Our findings, in a population of BCG-immunized children, do not lend support to the suggestion that infection with atypical mycobacteria is protective against childhood allergic disease.