Children who go to day care tend to get sick more often than those who stay at home. Some parents believe this is a good thing, thinking it makes children less likely to get certain sicknesses -- including allergies and asthma -- later.

But a new study said that is just wishful thinking. Any perceived protection disappears by the time the child hits age 8, the authors of the study said in a news release.

Researchers led by Dr. Johan C. de Jongste of Erasmus University in the Netherlands followed nearly 4,000 Dutch children for eight years. More than 3,500 of the children were assessed for specific allergies. Some also underwent testing for lung function.

The children were placed into three groups -- those who started day care before age 2, those who started later and those who didn't go.

The early starters were twice as likely to experience wheezing in their first year than those who didn't go. However, as the children aged, there was a shift. By age 5, there was a trend for less wheezing among early attendees.

The shift reversed itself by age 8, when there was no association between early day care attendance and wheezing at all.

Late day care attendees had similar effects, but they were not large enough to be considered statistically significant.

The bottom line, the authors wrote, is that the evidence didn't support the idea that going to day care helps prevent later illness.

"Early day care merely seems to shift the burden of respiratory morbidity to an earlier age, where it is more troublesome than at a later age," said de Jongste. "Early day care should not be promoted for reasons of preventing asthma and allergy."

The results were published in the Sept. 15 issue of the American Journal of Respiratory and Critical Care Medicine, a journal of the American Thoracic Society.