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World Asthma Day

Protective particulates

Munich, 05/06/2013

Growing up on a farm reduces the risk of asthma and allergies. Allergy specialist Erika von Mutius is studying why this is so, as the answer could suggest new ways of preventing such disorders.

Protective particulates

At the outset, Erika von Mutius dispels the notion that asthma and allergies are unpleasant but basically tolerable illnesses. As a pediatrician, von Mutius knows all too well that this is untrue. Children who develop these disorders “are really sick”, she says. Moreover, such ailments, which arise when the immune system fails to distinguish correctly between harmless and pathogenic agents, are a major public health problem and their incidence continues to rise. According to the Robert Koch Institute, some 17% of children in Germany suffer from bronchial asthma, neurodermitis, hay fever or food allergies. In the years 1994/95, it is estimated that one in ten children displayed symptoms of asthma; 20 years later, this figure had increased by 30%. The data for hay fever and allergenic skin disease show a similar trend. Strikingly, two centuries ago, hay fever was practically unknown.

Those are but dry statistics. But, as Chief of the Outpatient Clinic for Asthma and Allergies at Dr. von Hauner‘s Children‘s Hospital, which is part of Munich University Medical Center, Erika von Mutius is motivated by what she experiences on the wards. In her work as a physician, and as Professor of Pediatric Allergology at LMU, her primary aim is to find ways of helping sick children to cope with their condition, which often lasts a lifetime. For years she has been following up a lead – the so-called “farm effect” – which she hopes will guide her to that goal. The term refers to the observation that children reared on farms have a far lower risk of developing allergic disorders than city kids do. The so-called “hygiene hypothesis” explains this by postulating a link between exposure to a diverse population of microorganisms and reduced risk of autoimmune disease. As the saying goes, “a little dirt / does not hurt”.

In interviews, von Mutius says she is fascinated by the idea that aspects of one’s upbringing can protect one against asthma and other allergic conditions. Understanding the basis for this effect would allow us to apply it to children who have not been exposed to such an environment. Seen in this light, “our findings have an enormous preventive potential”, she says. Indeed, the German Research Foundation (DFG) has recognized the broad implications of her work by awarding a Leibniz Prize to her. The generously endowed accolade is conferred on only about a dozen recipients each year, and is regarded as the most prestigious German award for research.

Erika von Mutius became interested in the farm effect about 15 years ago, when she was looking for possible connections between air pollution and the prevalence of croup and allergies. She and her group, as well as workers in other laboratories, subsequently discovered that children brought up on farms are less likely to display symptoms of allergy than their playmates in the same village or children who live in towns. Indeed, the risk of developing asthma in an urban setting is twice as high. For hay fever, the effect is even more obvious; young city dwellers are three times more likely to contract hay fever than their country cousins.

In her studies, von Mutius identified two features of a rural childhood that help to build a kind of immunity to allergies and asthma. One is exposure to the air in cowsheds and barns from a very early age. The other is regular consumption of fresh, untreated milk. Both together reduce the risk that the immune system will overreact to innocuous stimuli: “So children who grow up on small dairy farms are least prone to allergic diseases.” Katrin Burger / Translation: Paul Hardy

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