London (PTI): Scientists have identified an "allergy gene" which more than doubles the risk of asthma, hay fever and eczema, a finding that could lead to new therapies to prevent allergies.

A team, led by the University of Edinburgh, has found that the filaggrin gene helps skin produce a protective barrier against the foreign bodies that trigger allergies, the British Medical Journal journal reported.

In fact, in their analysis of 24 previous studies, the scientists found that people with defects in this gene are much more likely to develop unwelcome reactions like sneezing and itchy eyes, dermatitis, asthma, hay fever and eczema.

The gene mutations also increased the risk of asthma in people with severe dermatitis, the findings revealed.

Lead scientist Prof Aziz Sheikh said: "What we found was a more than doubling in the risk of these allergies among people with this defect.

"These findings provide strong supporting evidence that, at least in a subset of those with allergic problems, the filaggrin gene defect may be the fundamental predisposing factor not only for the development of eczema but also for initial sensitisation and progression of allergic disease.

"Our finding suggests filaggrin is a robust biomarker for allergic conditions. What's striking is a high proportion of people who are getting eczema, it's an incredibly common disorder, and if the filaggrin gene is the major factor. It may be we can target it with drugs that can repair this protective skin barrier in due course."

Allergic responses are caused when the immune system wrongly identifies allergens such as dust mites, pollen, peanuts or cat hair as being dangerous. This triggers release of histamine in the body, which causes minor symptoms such as itching, wheezing, and sneezing but can also prove fatal.

Prof Sheikh was quoted by the British media as saying: "We call it the allergy march. It is an enormous problem and it is getting bigger all the time but in the future we hope we will be able to screen children at an early age for this gene defect and then start them on a programme of treatment."