We have also shown that Ascaris lumbricoides and Trichuris trichiura in this population are positively associated to IL-10 production by non-stimulated whole blood cells. In the present study, we investigated the effects of single and co-infections with intestinal parasites (A. lumbricoides and T. trichiura) and Toxocara spp. on the following outcomes: blood eosinophils total and allergen-specific IgE, skin reactivity to aeroallergen, atopic and non-atopic asthma and cytokine responses, in children living in poor neighborhoods of a Brazilian city.