Definition. Eosinophilia (e-o-sin-o-FIL-e-uh) is a higher than normal level of eosinophils. Eosinophils are a type of disease-fighting white blood cell. You can have high levels of eosinophils in your blood (blood eosinophilia). High levels of eosinophils may also occur in your body's tissues at the site of an infection or inflammation (tissue eosinophilia).