High levels of personal hygiene increase risk of asthma and eczema in infants

High levels of personal hygiene increase the risk of eczema and asthma, shows a study of almost 11000 infants in the Archives of Disease in Childhood.

The research focused on participants in a long-term study of parents and children (Avon Longitudinal Study of Parents and Children). Parents were surveyed about their children’s wheezy and eczema symptoms up to the age of 6 months, and then between 30 and 42 months.

A simple hygiene score was derived on the frequency of hand-washing, bathing, and showering, using responses to questionnaires when the children were 15 months of age.

For every unit increase in hygiene score, the likelihood of a child wheezing between the ages of 30 and 42 months increased by 4 per cent. In children under the age of 6 months, wheezing was partly explained by high levels of chemical products used to clean the home: certain strong chemicals are themselves known to irritate the airways, and so bias the findings.

But eczema was significantly associated with high hygiene scores, irrespective of the amount of chemicals used. And the association was even stronger for those children between 30 and 42 months, whose eczema was severe, with sore, weeping blisters. There was no difference in the frequency of hand-washing – a risk factor for the disease – between those children with more or less severe eczema.

The authors conclude: “ The importance of hygiene in public health should not be dismissed. However, the creation of a sterile environment through excessive cleanliness may potentially be harmful to the immune system.”