Respiratory Allergic Diseases such as allergic rhinitis and asthma are a major and growing issue of public health in Europe. Studies into the pathogenesis of allergic asthma and rhinitis have highlighted the importance of pathways leading to Th2-mediated inflammation. Th2 responses predominate in neonatal life; the normal immune maturation process results into Th1 responses dominating after the first years of life. However, influenced by genetic predisposition as well as environmental triggers, Th2-mediated responses persist in allergic individuals, often manifesting as asthma and rhinitis later in life. The timelines of Th2 to Th1 transition, occurring in healthy but not in atopic individuals, have not yet been fully determined. Recent studies have shown that "biological" age may determine when the symptoms of a disease will occur. These observations have stimulated research towards new biomarkers (including epigenetic factors) that may potentially predict, monitor and provide additional information on age-related disease development. The aim of iClock is to determine epigenetic maturation, assessed through whole genome methylation, throughout the life cycle in healthy and atopic individuals. This information with be associated with clinical and immunological parameters, to develop a model of age-dependent immune maturation and reliably describe an immunological clock. This will also explore the hypothesis that allergic diseases result from epigenetically-mediated defects in early immune maturation that may be reversed. The findings of the study may have major prognostic and therapeutic implications.