rom the New York University Department of Medicine suggests that the stomach bacterium Helicobacter pylori, which causes peptic ulcers and, potentially, stomach cancer, is also protective against asthma and allergy.

The study looked at the correlation between the presence of H pylori and a history of allergy in 7,663 adults who had been tested for the bacterium as part of America's Third National Health and Nutrition Examination Survey.

They found that an absence of H pylori colonisation correlates with a history of asthma and that this link is stronger in those whose asthma developed at an early age. Those who had H pylori were 40% less likely to have developed asthma by age 15 than those who tested negative for the bacterium.

When a subgroup of 2,386 adults who had been tested for H pylori were also subjected to skin-prick tests for six allergens, a similar pattern emerged. Those who tested positive for H pylori showed less sensitivity to the allergens, and the benefit was again most pronounced in the young.

These findings provide yet more support for the 'hygiene hypothesis', which suggests that the mass extinction of bacteria by means of excessive hygiene is upsetting the balance of health in humans.
Humankind has had a relationship with H pylori for 60,000 years and, only a few generations ago, between 70 and 90% of the population still had colonies of H pylori. Now, only about 10% of the US population has detectable levels of H pylori, and the figure is less than 5% in Germany and Sweden

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First Published in September 2007

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