Genes explain why first-born babies are more allergic

Wednesday May 21st, 2008

First-born children face an increased risk of developing asthma and allergy, according to a study of British children.

The research suggests that first-borns experience different conditions in the womb from their later siblings.

The team collected information on more than 1,200 newborns in the Isle of Wight, UK.

They tested the children's genes, and found that they often had a form of the gene called IL-13 which is linked to increased IgE in the blood.

Higher levels of IgE - an antibody - indicate an increased allergic response. When the children were tested at ages four and ten, they were more likely to have allergies than children who were not the first-born.

Researcher Dr Wilfried Karmaus of the University of South Carolina, USA, said: "This is the first study to test whether the effect of genes involved in the development of asthma and allergy differs between first- and later-born children.

"We were not surprised that birth order had an effect on the development of the immune system, but were surprised that this interaction persisted at least to age ten. Our findings add to the evidence that allergic reactions are programmed during pregnancy and then affect the disease in later life."

This could explain the increasing rates of asthma and allergies in children in the last 30 years, because of the falling birth rate, he added. It could also lead to "new and exciting avenues of intervention".

The findings will be presented today (May 21) at the American Thoracic Society's 2008 International Conference in Toronto, Canada.

Research presented at the American Thoracic Society International Conference, held in Toronto, Canada from May 16-21, 2008.

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