Child's Allergy Risk Higher If Parent Of Same Sex Has It

Researchers have discovered an interesting fact about the genetic basis of childhood allergic diseases: a child is more likely to have a particular allergy if his or her same-sex parent has it.

So for example, a girl's chance of having asthma is higher if her mother has it, and a boy's is higher if his father has it.

And the same appears to be true of eczema and other childhood allergies.

This is the conclusion of a study by Professor Hasan Arshad, a consultant in allergy and immunology at Southampton General Hospital, and colleagues, that is published in the August issue of The Journal of Allergy and Clinical Immunology.

What The Researchers Did

For the study, the researchers used data from the Isle of Wight (IOW) Birth Cohort Study, which collected information on just under 1,500 children that were followed up to the age of 18. During that time, the children were examined at age 1, 2, 4, 10 and 18.

The Isle of Wight, which lies off the South coast of England, is ideal for carrying out long-term prospective epidemiological studies because it has a stable resident population, so most of the participants did not move away during the course of the study, and were thus available for follow-up.

Arshad was one of the initiators of the The IOW cohort study, which was set up with the aim of prospectively studying a whole population (about 130,000 people live on the IOW) for the development of asthma and allergic diseases and identify any relevant genetic and environmental risk factors.

The data on the cohort contains detailed information on heredity and environmental exposures, collected from birth and updated at each follow-up, where detailed questionnaires were completed with the parents for each child, about asthma and any other allergies, for example eczema and rhinitis.

At ages 4, 10, and 18, the children also underwent skin prick tests to 14 common food and airborne allergens.

Other examinations included spirometry and bronchial provocation tests, and collected blood samples to measure Immunoglobulin E (IgE) at ages 10 and 18. IgE is an antibody that is often screened for in testing for allergies.

The parents also underwent assessments. For example, shortly after the children in the cohort were born, the researchers found out whether his or her parents had allergies, and the mother's IgE level was also measured.

What They Found

When they analyzed the results the researchers found that maternal asthma was tied to asthma in girls but not to boys, and paternal asthma was linked to asthma in boys but not to girls.

They found the same pattern for eczema: if a child's mother had eczema, then the chances of the child having it was higher if it was a girl but not a boy, and if the father had it, the chance was higher for his son but not his daughter.

Similar patterns were found for other allergies, as the authors explain:

"Similar trends were observed when the effect of maternal and paternal allergic disease was assessed for childhood atopy and when maternal total IgE levels were related to total IgE levels in children at ages 10 and 18 years."

Possible Implications

The authors suggest the findings may change the way childhood allergies are assessed and prevented. For instance, in diagnosis, it may be useful to find out the allergy history of the mother in girl patients and of the father in boy patients.

The study may also open new avenues for studying sex-dependent effects in hereditary diseases, with the prospect one day of finding ways to prevent them.

The National Institutes of Health in the US funded the study.