Allergic manifestations such as rhinitis, asthma and eczema are increasing all over the world and more steeply in western industrialized countries during the last few decades. The underlying causes are poorly understood. Genetic factors are unlikely to explain the increased prevalence of allergic diseases as genetic shift in the population cannot occur in such a short duration. Changes in lifestyle, living conditions, food
habits and environmental factors are implicated in the increased prevalence of allergic diseases.