Strong arguments for such an effect are the findings that relate early life day care attendance and increased number of older siblings to a significantly reduced risk of asthma in childhood and adolescence.

Furthermore, positive serologic immune responses to certain infections such as hepatitis A and Toxoplasma gondii have been found to be more common among non-allergic subjects. This suggests a role for such infections, or the lack of hygiene, to be operative in the inhibition of the development of allergic immune responses.

Children raised on farms who have frequent contact with animals such as cattle, pigs and poultry have been found to have very significant reductions in the prevalence of asthma and allergies.

This contact with farm animals exposes these children to a high and sustained load of microbial compounds such as endotoxins -- parts of the wall of gram-negative bacteria. These compounds have strong immunostimulatory effects that promote anti-allergic immune responses.

(Editor's Note: This story is based on an article, the first in the new series, "Infections: friend or foe in the development of asthma," starting this month in the European Respiratory Journal [ERJ].)

ERJ is the peer-reviewed scientific publication of the European Respiratory Society. The society's membership includes more than 5,000 specialists in lung diseases and respiratory medicine in Europe, the United States and Australia.


[Contact: Erika von Mutius]

01-Nov-2001