Exposure to farming in early life and development of asthma and allergy: across-sectional survey

Background A farming environment protects against development of asthma, ha y fever, and atopic sensitisation in children. We aimed to establish whethe r increased exposure to microbial compounds has to occur early in life to a ffect maturation of the immune system and thereby reduces risk for developm ent of allergic diseases. Methods We did a cross-sectional survey in rural areas of Austria, Germany, and Switzerland. 2618 (75%) of 3504 parents of 6-13-year-old children comp leted a standardised questionnaire on asthma, hay fever, and atopic eczema. Children from farming families, and a random sample of non-farmers' childr en, who gave consent for blood samples to be obtained for measurements of s pecific serum IgE antibodies to common allergens were invited to participat e (n = 901). Findings Exposure of children younger than 1 year, compared with those aged 1-5 years, to stables and consumption of farm milk was associated with low er frequencies of asthma (1% [3/218] vs 11% [15/138]), hay fever (3% [7] vs 13% [18]), and atopic sensitisation (12% [27] vs 29% [40]). Protection aga inst development of asthma was independent from effect on atopic sensitisat ion. Continual long-term exposure to stables until age 5 years was associat ed with the lowest frequencies of asthma (0.8% [1/122]), hay fever (0.8% [1 ]), and atopic sensitisation (8.2% [10]). Interpretation Long-term and early-life exposure to stables and farm milk i nduces a strong protective effect against development of asthma, hay fever, and atopic sensitisation.