Therefore, the high prevalence of asthma that is currently observed in some urbanized zones of the tropics, where helminth infections, such as ascariasis, are still present but with less intensity than in the past, may be explained, among other factors, as a consequence of the particular historical moment of the ancient and complex relationships between parasites and the immune system: a point where, because of several reasons, the immunostimulating effects of helminths on the IgE responses predominate. This evidence concerns the gene IGHE and ascariasis.