Eosinophilia (e-o-sin-o-FILL-e-uh) is a higher than normal level of eosinophils. Eosinophils are a type of disease-fighting white blood cell. This condition most often indicates a parasitic infection, an allergic reaction or cancer.
You can have high levels of eosinophils in your blood (blood eosinophilia) or in tissues at the site of an infection or inflammation (tissue eosinophilia).
Tissue eosinophilia may be found in samples taken during an exploratory procedure or in samples of certain fluids, such as mucus released from nasal tissues. If you have tissue eosinophilia, the level of eosinophils in your bloodstream is likely normal.
Blood eosinophilia may be detected with a blood test, usually as part of a complete blood count. A count of more than 500 eosinophils per microliter of blood is generally considered eosinophilia in adults. A count of more than 1,500 eosinophils per microliter of blood that lasts for several months is called hypereosinophilia.