The intestinal microflora in allergic Estonian and Swedish 2-year-old children

Epidemiology must surely hold the key to discovering the environmental eauses of asthma [1] but a clear explanation for the epidemic rise in asthma in developed countries over the last 30 years still eludes us. Certainly, changes in the prevalence of known risk factors appear to have played only a small part [2] and new aetiological hypotheses are needed.