University of Dundee

Gene identified as a cause of peanut allergy

14 Mar 2011

An international collaboration led by the College of Life Sciences at the University of Dundee has made a significant breakthrough in understanding the causes of peanut allergy.

Peanut allergy affects 1-2% of children in the UK and may result in a severe or life-threatening allergic reaction. The number of people affected by peanut allergy has increased dramatically over the past 20-30 years, but the causes of the disease are unknown.

Now the collaboration led by researchers in the Division of Molecular Medicine at the College – working with colleagues in Canada, Ireland, England, and the Netherlands - has identified a gene defect that can triple the risk of a child developing peanut allergy. The gene responsible – Filaggrin – has previously been shown by the Dundee team to be a significant factor in causing eczema and asthma.

“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,” said Dr Sara Brown, Wellcome Trust Intermediate Clinical Fellow in the Division of Molecular Medicine at Dundee.

“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.

“Now, for the first time, we have a genetic change that can be firmly linked to peanut allergy.”

The findings are published in the Journal of Allergy and Clinical Immunology.

The Filaggrin gene codes for a protein that helps to make the skin a good barrier against irritants and allergens. Changes in the gene decrease the effectiveness of this `barrier’, allowing substances to enter the body and leading to a range of allergic conditions.

The study has found that one in five of all peanut allergy sufferers have a Filaggrin defect. Those with the defect can be three times more likely to suffer peanut allergy than people with normal Filaggrin.

“We knew that people with a Filaggrin defect were likely to suffer from eczema, and that many of those people also had peanut allergy,” said Professor Irwin McLean, one of the world’s leading authorities on Filaggrin, Head of the Division of Molecular Medicine.

“What we have now shown is that the Filaggrin defect is there for people who have peanut allergy but who don’t have eczema, which shows a clear link between Filaggrin and peanut allergy.

“The Filaggrin defect is not THE cause of peanut allergy but we have established it as a factor in many cases. We don’t yet know enough about the causes of peanut allergy but this is an important step forward.”

Professor McLean said the Filaggrin findings suggest that peanut allergy may be caused by substances entering the body through the skin, though it could also have an effect in the gastro-intestinal area.

He also stressed that as Filaggrin defects were found in only 20% of the peanut allergy cases there is still a lot of work needed to fully understand the genetic risk factors for this complex disease.

The collaboration looked at four different population groups, in Canada, England, Ireland and the Netherlands. This is the first time that any genetic association with peanut allergy has been demonstrated in more than one population, making it more likely to be a genuine risk factor.