The same allele has been linked to asthma susceptibility in a number of studies, mostly in Eurasian populations (Wang et al., 2004; Gervaziev et al., 2006; Kabesch et al., 2006; Chiang et al., 2007; Li et al., 2008; de Guia and Ramos, 2010; Berenguer et al., 2012) likely a side-effect of IL4 positive selection, acting not only over genetic and environmental factors, but also over epigenetic signatures shaped through time. This evidence concerns the gene IL4 and asthma.