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A dose of dirt to boost your immunity

health and fitness Updated: May 04, 2008 00:23 IST
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Everywhere you go, you run into people wheezing, sniffing, coughing or gasping, which makes you wonder whether anyone is really safe from asthma. Apart from the usual triggers such as air pollution and pollen, research has consistently shown that food colour, food additives, obesity, secondhand smoke, poorly ventilated homes and workplaces (10 per cent of adult asthma is work-related), fumes, stress, cold weather, domestic violence and even relationships breaking up, become asthma triggers in people with sensitive (hyperallergic) airways.

So what makes airways sensitive? It’s all about how your immune system reacts to what it considers an assault on the body. An asthma attack occurs when an allergen or another stress factor causes an immune reaction that leads to inflammation (swelling) in the airways. The airways get constricted, narrowing air passage and reducing air flow in the lungs. This causes wheezing, shortness of breath, chest tightness, and coughing. Asthma attacks can last for a few minutes to days and can become life-threatening if not treated.

It’s perhaps not surprising that more and more airways are buckling under the combined attack of so many new triggers. But then again, no one has convincingly explained why people in more sterile environments have higher incidence of asthma than others who live in badly ventilated hovels that they share with dust, mites, pets and people with suspect hygiene.

There is a popular hygiene hypothesis that blames increasing asthma cases to the growing lack of exposure to bacteria and viruses in early childhood, which it says prevents the body from developing a healthy immunity. I don’t quite buy this, mainly because this theory should mean that children who have been ill very often in early childhood would have a lower risk of asthma in later life. The reverse is true. Overuse of antibiotics in early childhood actually increases risk of asthma in later life.

What is more convincing is the modified hygiene hypothesis, which says that more than exposure to germs and organisms that cause disease, it is exposure to harmless bacteria and fungi found in dirt and vegetation that makes the immune system healthy and prevents it from overacting to allergens. Earlier this week, two large studies supported this theory. One, from the University of Columbia in the US, found asthma cases went down by 25 per cent among children who lived in neighbourhoods with lots of trees. Another, from the Institute of Epidemiology in Munich in Germany, used blood test reports to confirm yet again that having a dog in the house boosts children’s immune system, as opposed to children suddenly exposed to inhaled allergens such as house mites and pollen.

Earlier studies have also shown that living in farms among animals, having many older siblings and attending day care at an early age offer protection against asthma, most likely because all these situations translate into more exposure to germs — both good and bad — in early childhood.

This celebration of germs and dirt is likely to make you wonder, how dirty is too dirty? It is premature to advocate giving children dirt or germ pills for breakfast, but don’t worry about an occasional slush football or romp in the park with the family pet as long as they wash up —the children not the dogs — before meals. Whenever you feel squeamish, just remind yourself it’s all about strengthening up their immunity.