Tissue eosinophilia. Coloured scanning electron micrograph (SEM) of an eosinophil from a patient with eosinophilia. Eosinophilia (that is, an increased number of eosinophils) can be found both in the peripheral blood and/or in tissues in several disorders, including helminthic parasite infections, atopic and allergic diseases as well as adverse drug reactions. Tissue eosinophilia usually results from increased recruitment of activated eosinophils from the bloodstream. Once recruited into tissues, activated eosinophils have the capability to cause tissue damage and dysfunction. Magnification: x8000 when printed at 10 centimetres wide.