Eosinophilia (e-o-sin-o-FILL-e-uh) is the presence of too many eosinophils in the body. An eosinophil is part of a group of cells called white blood cells. They are measured as part of a blood test called a complete blood count. This is also called a CBC. This condition often signals the presence of parasites, allergies or cancer.

If eosinophil levels are high in the blood, it is called blood eosinophilia. If the levels are high in inflamed tissues, it is called tissue eosinophilia.

Sometimes, tissue eosinophilia may be found using a biopsy. If you have tissue eosinophilia, the level of eosinophils in your blood is not always high.

Blood eosinophilia can be found with a blood test such as a complete blood count. Over 500 eosinophils per microliter of blood is thought to be eosinophilia in adults. Over 1,500 is thought to be hypereosinophilia if the count remains high for many months.