MedWire News: Results of a study conducted in eastern Europe support the theory that children who grow up in sanitised environments face an increased risk of allergic conditions such as hayfever and asthma.
Writing in the journal Clinical and Experimental Allergy, Dr Michael Kramer (The Montreal Children’s Hospital, Quebec, Canada) and team explain: “Despite the increasing prevalence of asthma, hayfever, atopic eczema, and certain food allergies in most Western industrialised countries over the last several decades, the prevalence of allergic disease has remained low in Eastern Europe.”
They add that one of the explanations offered for this East–West difference is the hygiene hypothesis. According to this theory, children who are brought up in overly hygienic environments do not have the opportunity to develop sufficient immune system resistance to the development of allergic diseases.
To investigate factors associated with risk of allergic diseases, Dr and team monitored 13,889 children in Belarus up to the age of 6.5 years. Data on allergic symptoms and diseases were collected along with results of skin-prick tests for five common airborne allergens (house dust mite, cat, birch pollen, mixed Northern grasses and Alternaria). Parents were also asked about their child’s exposure to farm animals, pets and probiotics, and whether they had wheezed or shown signs of allergies.
The researchers found that boys, children with a family history of allergies and those who had taken probiotics were more likely to have wheezed or suffered from hayfever symptoms over the previous year than other children.
Children with mothers who smoked were also more likely to wheeze or have hayfever than those with non-smoking mothers.
In contrast, pet ownership, contact with farm animals and having siblings were associated with a reduced risk of allergic symptoms. Children who lived in rural areas of Belarus were also less likely to have allergies than those from urban areas.
Contrary to results of other studies, exclusive breastfeeding was not associated with a reduced risk of allergies in children, notes the team.
Dr Kramer and team conclude: “Many of the risk and protective factors we identified are consistent with those reported in Western countries and with the hygiene hypothesis.
“Further research on dietary and other environmental and genetic factors is necessary to understand the low prevalence of allergic disease in Belarus and other Eastern European countries.”
Commenting on the findings, Dr Elaine Vickers, from Asthma UK, said: “The hygiene hypothesis is a hot topic of debate in the research community. Some believe that our immune system, which is primed for fighting off a wide range of infections, somehow goes awry in our modern, sanitised environment, leading to increased rates of allergies and asthma. Others believe that it’s more to do with our genetic makeup and the number of severe viral infections we experience as a child.
“Whatever the truth, the best advice we can currently give to parents is not to smoke around their children and make sure they have a balanced diet and get plenty of exercise.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009
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