Immunoglobulin E (IgE) is a kind of antibody that has only been found in mammals. IgE’s main function is immunity to parasites such as helminths like Schistosoma mansoni, Trichinella spiralis, and Fasciola hepatica. IgE is utilized during immune defense against certain protozoan parasites such as Plasmodium falciparum. IgE also has an essential role in type I hypersensitivity, which manifests various allergic diseases.

There is much speculation into what physiological benefits IgE contributes, and, so far, circumstantial evidence in animal models and statistical population trends have hinted that IgE may be beneficial in fighting gut parasites such as Schistosoma mansoni, but this has not been conclusively proven in humans. Epidemiological research shows that IgE level is increased when infected by Schistosoma mansoni, Necator americanus, and nematodes in human. It is most likely beneficial in removal of hookworms from the lung.