OXFORD researchers have found children are more likely to inherit asthma and hay fever from mothers than fathers. The gene responsible, found on chromosome 11, is only active when inherited from the mother.

An international team of scientists, led by Bill Cook and Julian Hopkins, speculates that maternal inheritance of asthma and hay fever may be caused by a mechanism called genetic imprinting. The mother may influence the development of the child's immunity whilst the child is still in the womb, when some of her antibodies and what she eats passes through the placenta to the foetus. Antibodies present in breast milk can also influence a child's immune system, sometimes increasing the chance of developing allergies.

Earlier research by Cookson's team had shown that asthma and allergies run strongly in families.