The authors of a study from The University of Arizona claim they have proved that infections early in life prevent asthma. They haven't.

Children who have older siblings are more likely to wheeze before age five, and these same children are far less likely to wheeze after age six. This tells you that having an older brother or sister exposes a child to earlier and more frequent infection that can cause wheezing, but these same children then are far less likely to wheeze after age six.

Consider that these children have siblings who bring them infections from school so they catch infections early and many infections cause wheezing in young children. Then when they start school and are exposed to many germs from their classmates, they are immune to infections that cause wheezing so they are less likely to wheeze.

NEJM August 24, 2000

Checked 8/9/05

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