The effects of farming and birth order on asthma and allergies.

A farm childhood is apparently protective in allergic disease, but studies of this issue in Europe have been confined to particular types of farming practice. This study addressed whether or not this effect was generalisable. A cross-sectional survey of 800 schoolchildren living in rural Crete was undertaken. Standard questions relating to allergic disease were included and atopy was measured through skin-prick tests involving 10 local aeroallergens. The prevalence of atopy was 24%, but associated symptoms were far less common. At all ages, children from farming families had more frequent contact with farm animals (mainly goats), but were no less likely to be atopic. Atopy and seasonal rhinitis were significantly and independently more common among first-born children. This community has an intermediate prevalence of atopy but a very low frequency of allergic disease; farming does not seem to be an important determinant, possibly because it is of the wrong sort. Thus farming effects may be specific to local practices. First-born children in this community also appear to be at increased risk of allergic disease.

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.