The recent theory that children who come into contact with disease early on will be protected from infections and allergies in later life is a myth, research suggests.
Scientists at the Erasmus University in the Netherlands are now challenging the “hygiene hypothesis” that early exposure to microbes somehow strengthens the immune system against allergies.
Previous studies suggested that youngsters exposed to bugs by older siblings or attending nursery had a reduced risk of developing allergies.
However, a study published by the American Thoracic Society found although children in day care got more colds and other infections, they were just as likely as other children to go on to develop asthma or another allergy by the age of eight.
After studying 4,000 children, researchers concluded that youngsters with siblings or those who went to nursery were four times as likely to develop frequent chest infections and had double the risk of wheezing in early life than those who did not, with no obvious pay off in terms of later protection from allergy.
Writing in the American Journal of Respiratory and Critical Care Medicine, the authors suggested the infections may, in fact, do more harm than good.
Lead author Dr Johan de Jongste, said: “Early day care should not be promoted for reasons of preventing asthma and allergy.
“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.”