Childhood infections don't stop adult allergies and asthma"Hygiene hypothesis" challenged
Cases of asthma and allergies have exploded in the last 50 years. Reasons put forward to explain this include the so-called " hygiene hypothesis - modern hygienic lifestyles mean that children are too clean and have not encountered enough germs early on in life.
But now new research appears to disprove this theory. Being exposed to common childhood infections at nursery does not lower the risk of developing allergies and asthma later on in life according to the study.
Previous studies suggested that young children who encounter bugs and infections at an early age through attending playgroups nurseries or from brothers and sisters were at a lower risk of developing asthma and allergies as adults.
In fact it seems that such children experience more breathing problems when younger, with no benefit when they grow up.
The study looked at nearly 4,000 Dutch children attending day care over an 8 year period. Very young children without older siblings were found to have more breathing problems up to the age of 4, but these fell away by the age of 8.
"Early day care was associated with more airway symptoms until the age of four years, and only in children without older siblings, with a transient decrease in symptoms between four and eight years" said leader of the study Johan C de Jongste.
"We found no evidence for a protective or harmful effect of day care on the development of asthma symptoms, allergic sensitization, or airway hyper-responsiveness at the age of eight years" he continued.
Despite the widespread acceptance of the idea that these early exposures pay off in later health benefits, the data in this study do not support that belief. If anything, this study suggests that these exposures cause more airway symptoms early in life with no counterbalancing benefit later.
"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 Dr. de Jongste. "Early day care should not be promoted for reasons of preventing asthma and allergy."
The results are published in the American Journal of Respiratory and Critical Care Medicine, a journal of the American Thoracic Society.
This article was published on Wed 9 September 2009
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