A farming environment protects against development of asthma, hay fever, and atopic
sensitisation in children. We aimed to establish whether increased exposure to microbial
compounds has to occur early in life to affect maturation of the immune system and
thereby reduces risk for development of allergic diseases.
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 completed a standardised questionnaire
on asthma, hay fever, and atopic eczema. Children from farming families, and a random
sample of non-farmers' children, who gave consent for blood samples to be obtained
for measurements of specific serum IgE antibodies to common allergens were invited
to participate (n=901).
Exposure of children younger than 1 year, compared with those aged 1-5 years, to stables
and consumption of farm milk was associated with lower frequencies of asthma (1% [3/218]
vs 11% [15/138]), hay fever (3%  vs 13% ), and atopic sensitisation (12% 
vs 29% ). Protection against development of asthma was independent from effect
on atopic sensitisation. Continual long-term exposure to stables until age 5 years
was associated with the lowest frequencies of asthma (0.8% [1/122]), hay fever (0.8%
), and atopic sensitisation (8.2% ).
Long-term and early-life exposure to stables and farm milk induces a strong protective
effect against development of asthma, hay fever, and atopic sensitisation.