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Project - Background

Allergy has developed into a major health concern in Europe with over 80 million people affected by some form of allergic disease and with around 30 million people suffering from asthma. Allergic diseases can currently be managed effectively but not cured. They diminish patients’ quality of life and have considerable socio-economic costs, such as health care utilization, medication, and school or work days missed. More and more people are developing allergic diseases and it is estimated that, by 2015, one in two Europeans is likely to suffer from at least one form of allergy (www.ga2len.net).

The incidence of allergic diseases is highest early in life. IgE antibodies directed against dietary allergens can already be detected shortly after birth. There is a progressive increase in the incidence of atopic sensitisation over childhood and adolescent years, yet the best predictor for later incidence is manifest atopic sensitisation in the first 3 years of life. Atopic eczema is manifesting in the first year of life in a significant proportion.. Likewise, most children with asthma start wheezing in the first 1-3 years of life. However, not all children wheezing in the first years of life will go on to develop asthma. Only a prospective assessment of symptom progression with objective measures of lung function and airway inflammation will allow the identification of childhood asthma cases with reasonable certainty. 

Any dietary, life style or environmental determinant of allergic disease must therefore occur before the first manifestation of illness and before the conclusive maturation of the immune system. Environmental exposures such as the living environment, dietary habits, or microbial exposures are likely to play a significant role when occurring early in life or during pregnancy. Allergic diseases are believed to be determined by multiple factors, including gender, race and genetic predisposition. A number of protective dietary and environmental candidate exposures have been identified in cross sectional surveys, but their causal contribution cannot be assessed with certainty, because the temporal relation between exposure and onset of illness remains ill defined. Several studies across rural areas in Europe have consistently demonstrated that children raised on farms are less likely to develop atopic sensitization, hay fever, wheeze and asthma. Although different sources of protection within the farm environment, such as consumption of raw farm milk, exposure to livestock, and some animal fodder may confer protection, the exact nature of the biologic substances involved in protection are still unknown.

 Furthermore, the mechanisms by which such exposures impact on a child’s immune response ultimately resulting in aberrant and exuberant reactions towards normally well tolerated environmental exposures remain largely unknown. Therefore, only birth cohort studies across rural areas in Europe enrolling children during pregnancy and including investigations of mechanistic pathways will allow adequate evaluation of exogenous factors for the incidence of allergic diseases by linking the exposure to the development of allergic illness in a given child.