Why So Many Allergies – Now?
It’s a great question.
And a big question.
It’s the answer that’s not as simple.
Intro:
If you have a child with peanut allergies, other parents will say to you: “Nobody was allergic to peanut butter when I was a kid.” If a cat swishing through a room starts you wheezing, you’ll get asked: “How come so many people have asthma?” Both are reasonable queries, variants on the broader million-dollar question: “Why do so many people have allergies today?”
If you want an easy answer, allergy experts will simply say they don’t know. But what they mean is – they don’t know entirely. The fact is that scientists understand a lot more about allergic disease than they did a decade ago. They know, for instance, that genetics aren’t the whole story. Allergy begins with an inherited tendency, but whether that gets switched on to full-blown allergic disease may well depend on where and how you grew up, and on what you breathed. It appears a complex interplay of factors either promotes or protects against allergy in its many guises – asthma, food allergy, rhinitis or eczema.
Scientists still have gaping holes in their knowledge, but as they continue to fill in the pieces to the puzzle, what they are finding is fascinating and often surprising. In the following investigation, Allergic Living examines what science knows so far about why allergies occur.
Excerpt:
While references to asthma date back to ancient Chinese medical texts, the real story of our modern understanding of allergy begins in earnest in 1989. It was a heady year, with the fall of Berlin Wall and the beginning of the opening up of the former East bloc. A team of German scientists decided this presented a great opportunity to compare the prevalence of asthma in Leipzig (former East Germany) and Munich (former West Germany). Here were two highly similar gene pools of people who had been living in very different societies and conditions. “At that stage, everyone, including us, believed that air pollution was causing asthma and allergies,” says Dr. Erika von Mutius, who was then a young pediatrician and team leader, and who today is a professor and head of the asthma and allergy department of Munich University’s Children’s Hospital. When the findings began coming back showing that there was considerably more asthma in modern, Western, hygienic Munich than among the study group living in Leipzig with its billowing factory smokestacks, the researchers were incredulous.
“It was so opposite what we’d anticipated,” recalls von Mutius on the phone from Munich. “We didn’t believe it, so we thought it was a mistake in data entry and re-entered all the data.”
But the data were right, and the results were published in 1992. That year, von Mutius took her research with her to Tuscon, Arizona, where she worked on a fellowship at the University of Arizona under her mentor, Dr. Fernando Martinez, the well-known asthma researcher who today is the director of the Arizona Respiratory Center. One day he read a medical paper out of Britain about something called “the hygiene hypothesis”. The author of that paper, an epidemiologist named David Strachan, had conducted a study of over 17,000 British children and found that youngsters who had older siblings and were exposed to more infections and bacteria early in life were less likely to develop hay fever or eczema. Writing in that same pivotal year of 1989, Strachan had theorized that smaller family sizes and higher levels of hygiene in modern Western homes may have been contributing directly to the increased prevalence of allergy.
Martinez was intrigued. What, he asked, would happen if von Mutius took into account the sizes of her East German and West German families? The data were incomplete, but it was the less allergic East Germans who clearly had more children per family. She and Martinez followed up with a study comparing family sizes and allergy in Munich and Leipzig (and a neighbouring city). A pattern emerged: the most allergic were the Munich kids with one or no siblings; the least allergic were the East Germans with two or more brothers and sisters. Children in the larger families were being exposed to more germs. It fit with this rudimentary hygiene hypothesis. “It took off from there,” says von Mutius.
Back to the Land
Where the hygiene theory took off to was a place caught in a time warp: the traditional European farm, where father, mother and children still do all the manual labour, from milking to sweeping out the stables. The idea to look at the family-run farm actually came from a school doctor in a Swiss village. He noticed that farm children under his care, unlike other kids, never seemed to get hay fever. Struck by this observation, he began writing to allergy experts in Basel, research colleagues of von Mutius. At first they were skeptical of the rural doctor’s notion, but then a few Swiss professors ran a small study. The findings were compelling: there was markedly less allergy and asthma on the farms in question. This merited further examination.
And so in 1998, von Mutius began her long-running involvement in a series of European farm studies that have become the underpinning of current allergy research. The first was ALEX (the Allergy and Endotoxin Study), involving scientists from Germany, Austria and Switzerland. The team began gathering and publishing data, and the central findings were consistent: children who lived on these farms were significantly less inclined to have allergies and asthma than children in the neighbouring village. Then came other major studies of the family farms: the multi-centre PARSIFAL study of children enrolled in Steiner schools (akin to Waldorf education), which involved 6,600 pupils in five countries; and the PASTURE study, which examined children’s exposure to microbes on farms across Europe. With each study, with each new set of samples of stable and mattress dust, with each new set of blood-test results for environmental and food allergies, a little more was known. “We are getting somewhere,” says von Mutius, taking stock for a moment. “There are now 17 papers [since 1999] that all show the same things.”
They reveal what’s termed “the farming effect,” a phenomenon that protects against allergic disease. Von Mutius and her colleagues have narrowed the effect down to three key factors: livestock (specifically cows, pigs or poultry); type of fodder (for instance, whether it’s fresh grass or hay); and drinking of raw farm milk. The findings have been generally consistent – about 1 to 2 per cent of the farm children in the studies had asthma compared to 12 per cent of local, non-farm children in control groups. “I’m completely convinced that this is real,” says von Mutius.
Excerpted from the Fall 2008 issue of Allergic Living magazine.
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