Children with a certain gene defect are more likely to develop a peanut allergy, an international study suggests.

Researchers studied the effect of changes in the gene filaggrin, which helps the skin block out allergens. Changes in the gene were already thought to reduce the effectiveness of the barrier, increasing the risk for eczema and asthma, say the U.K., Dutch and Canadian the researchers.

Now, such changes appear to raise the risk of peanut allergy as well, said the team, whose work is published in the March issue of the Journal of Allergy and Clinical Immunology.

"It was a logical next step to investigate whether filaggrin may also be a cause of peanut allergy, since a child may develop all three of these diseases together," Dr. Sara Brown of the division of molecular medicine at the University of Dundee said in a release.

"Allergic conditions often run in families, which tells us that inherited genetic factors are important. In addition to that, changes in the environment and our exposure to peanuts are thought to have been responsible for the recent increase in peanut allergy seen in the Western world in particular."

The team's findings suggest one in five peanut allergy sufferers has a filaggrin defect, which means it is not the only cause of peanut allergies, said Prof. Irwin McLean, a study co-author also based at Dundee in Scotland.

But people with the defect are three times more likely to suffer a peanut allergy than people with normal filaggrin, the researchers reported.

The study looked at 71 English, Dutch, and Irish patients with positive peanut results in an oral food test, where the patient eats the food while a physician watches carefully for symptoms. Their genetic findings were compared with 1,000 controls from the English population.

The investigation was then repeated in 309 Canadians with peanut allergies — defined by a food challenge, clinical history or skin prick test — and another 891 controls from the general Canadian population.

"Taken together, our experimental data from four populations of European origin demonstrate a strong and significant association of loss-of-function mutations within the filaggrin gene with clinically significant peanut allergy," the authors concluded.

It's estimated about one in 50 Canadian children has a peanut allergy, and about one to two per cent of these can have severe or life-threatening reactions, according to Anaphylaxis Canada.

The Canadian peanut allergy study was supported by grants from the Canadian Dermatology Foundation, the University of Saskatchewan, Department of Medicine Research Fund, the Foundations of the McGill University Health Centre and the Montreal Children's Hospital as well as grants from the Canadian Allergy, Asthma, and Immunology Foundation and the AllerGen Network of Centres of Excellence.