(Paris-AFP) - Suspicions that genes play a part in peanut allergy were confirmed in a study Tuesday that said environmental factors may contribute to the problem.
Researchers in the United States compared the genomes of more than 1,300 children of European ancestry, most of whom had some kind of food allergy, to those of their biological parents.
The team found no genetic variants to explain allergies to eggs or cow's milk.
They did, however, find that telltale variants in two genes, HLA-DQ and HLA-DR, located on Chromosome 6, accounted for about 20 per cent of children with peanut intolerance.
"We always suspected it, but this is the first genome-wide association study that identified a genetic link," said Xiaobin Wang, a professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.
In the United States, about one child in 13 has a food allergy, of which the most common by far is to peanuts, according to the study published in the journal Nature Communications.
The problem ranges in scale from a lifestyle hassle to life-threatening. Those with a severe allergy live in constant fear of accidental exposure to peanuts.
"Over the past 20 years, FA (food allergy) has grown from a relatively uncommon to a major clinical and public health problem worldwide, due to its increasing prevalence, potential fatality and enormous medical and economic impact," the study said.
"FA accounts for more than $20 billion (17.7 billion euros) in overall annual healthcare costs in the United States."
The investigation marks a first step towards a fuller picture of genetic causes for food allergies, something that would help doctors identify children at risk.
The researchers added there could also be non-genetic factors.
Not everyone with the HLA-DR and HLA-DQ mutations develops peanut allergy, they found.
It could mean other culprits are epigenomes -- the chemical switches which help turn genes on and off.
Epigenomes are not part of DNA but are passed on as cells divide. They can be influenced by environmental factors, such as food, tobacco smoke, toxic substances and uterine fluid.
On Monday, a paper in the New England Journal of Medicine found that most children at high risk from peanut allergies -- determined by pre-existing eczema or egg allergy -- were protected if they ate peanuts frequently, starting within the first few months of life.
"Hopefully, one day, we can manage or prevent food allergies in a safe, simple, effective way," Wang said.
"We might be able to use pharmaceutical treatment, but if we can figure out whether a lifestyle, nutrition or environmental change could reduce allergies, that would be even better."
