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allergies

These 41 hay fever genes can’t explain allergy ‘epidemic’

Scientists have mapped 41 genes that increase the risk of developing hay fever, in a new study of almost 900,000 people. Of the genes, 20 are new to science.

The findings bring researchers a little closer to understanding the causes of hay fever, which is the most common type of allergy. It affects more than 400 million worldwide.

“This is the largest genetic study ever conducted into hay fever,” says Klaus Bønnelykke, clinical research associate professor of clinical medicine at the University of Copenhagen.

“The risk genes we have mapped can help us understand what causes hay fever. And in the longer term this will be helpful when it comes to developing drugs and better treatments for the allergy.”

Why are there more and more sufferers?

Airborne allergens such as pollen, pet hair, and dust mites trigger hay fever. The number of people with allergies is increasing, particularly in western countries. It is not yet known exactly why hay fever is beginning to reach epidemic proportions, but it seems likely that part of the explanation lies in our lifestyles, Bønnelykke says.

“Genes are very important, and twin studies show that in more than half of sufferers, the allergy is caused by genetics. We can also see that a great many cases must be due to environmental factors, since the number of people with hay fever has increased over the past 100 years.

“The allergy is not spreading that fast due to genetic changes. It takes tens of thousands of years for genetic makeups to change. Therefore, I believe that the rise is likely to be caused by an interplay between risk genes like the ones we have found in this study and various environmental factors that trigger the allergy in people with risk genes,” he says.

Links with other diseases

The study does not explain why some people develop hay fever and others don’t. It only explains about 10 percent of the illness. Therefore, the next step, Bønnelykke says, is not only to add more participants, but also to start looking at how the genes interact with environmental factors such as pollen, pollution, and pets.

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The findings also show an overlap between risk genes for hay fever and risk genes for autoimmune diseases such as type 1 diabetes, rheumatoid arthritis, and inflammatory bowel disease. As with allergies, the number of people with autoimmune diseases has risen sharply in recent years. The overlap of genes can help explain why, Bønnelykke says.

“Our study helps identify genetic commonalities which may be a key to understanding why these illnesses are all on the rise. It seems there are some common factors in the western lifestyle that are causing these illnesses to become more widespread, but we haven’t yet understood why.

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“The genetic overlap we have observed seems to suggest that it is the same genes that trigger these illnesses, at least in part. This is important information when trying to understand the mechanisms and causes. It may matter not just to understanding hay fever but also to understanding autoimmune diseases.”

Other researchers from the University of Copenhagen contributed to the study, which appears in Nature Genetics. The Lundbeck Foundation, the Danish Ministry of Health, the Capital Region of Denmark, the Novo Nordisk Foundation, and Independent Research Fund Denmark funded the work.

Source: University of Copenhagen

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