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Parasites may protect against allergies – the hygiene hypothesis vindicated |
An analysis of 21 studies on almost 29,000 people, mostly children, from South America, Africa, Cuba, Vietnam and Turkey has found that the participants with any parasitic infection were 31% less likely to have a reaction when exposed to common allergens like the dustmite or cockroach proteins in a skin test. The findings give some credence to the ‘hygiene hypothesis’, which proposes that our increasingly clean lifestyles may be contributing to the worldwide increase in allergies and asthma. It is suggested that exposure to viruses and bacteria in early life can increase the strength of the immune system, and decrease the likelihood of the immune system overreacting to benign substances. But findings thus far are conflicting. The majority of the participants in the study, led by Dr Johanna Feary and colleagues at the University of Nottingham, UK, were infected with the geohelminths family of parasites which includes hookworm, roundworm and whipworm. (See John Scott’s account of his experiences using helminths to counter his long history of allergy.) Even though these findings do not prove that intestinal parasites are protective against allergies, and even though eradicating parasites in developing countries remains an important goal, Feary cautions that eradicating such infections could have the unintended effect of increasing allergy rates in developing countries – where health services are already overstretched. Further research on the relationship between the two is still very much needed, and understanding how environment affects allergy worldwide has become increasingly important. Allergy - November 2010 First published in December 2010
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