The formation of IgE antibodies against environmental allergens represents the hallmark of type I allergy. Data from in vitro cultured cells and experimental animal models provide controversial evidence for isotype switching from IgM to IgE production via sequential as well as non‐sequential (i.e. direct) class switch. We analyzed the evolution of IgE responses in 11 children developing birch pollen and/or grass pollen allergy during the first 7 years of life using purified recombinant allergen molecules (major birch pollen allergen, Bet v 1; major timothy grass pollen allergens, Phl p 1, Phl p 2, Phl p 5). Demographic, clinical and serological data indicated a postnatal sensitization to pollen allergens. A parallel development of IgG1–4 and IgE responses to recombinant allergen molecules compatible with a strictly sequential class switch to IgE was observed only in one child. The only partly synchronized and dissociated development of allergen‐specific antibody responses found in all other cases can be best explained by a partly sequential class switch involving few switch stations or, more likely, by direct class switching. Kinetics and courses of allergen‐specific antibody responses (IgM, IgG1–4, IgE) during the first years of life suggest that, once established, allergen‐specific IgE responses are driven by antigen contact rather than by cytokines controlling class switch to IgE.