In particular, the FCER1A gene encodes the Fc fragment of IgE and FCER1A polymorphisms are associated with IgE levels38; as IgE levels are associated with the response against a range of infections by parasitic worms (helminths), it is largely accepted that IgE levels have been under selective pressure to help counter metazoan parasites37 during human evolution. Here, FCER1A is linked to infection.