Various health conditions can cause eosinophilia. Some of the top causes include an infection from a parasite, an allergic reaction or cancer. Eosinophilia can lead to high levels of eosinophils in the blood. Or it can lead to high levels of eosinophils in tissues at the site of an infection or at the site of swelling called inflammation.

Eosinophilia doesn't have clear-cut symptoms. But the medical conditions that can cause eosinophilia can bring on various symptoms. A health care checkup for those symptoms often leads to eosinophilia being found by blood tests. Sometimes, a very high level of eosinophils in the blood can damage organs. This is called hypereosinophilic syndrome.

Treatment for eosinophilia depends on the condition that causes it. If the underlying condition can be found and treated, eosinophilia likely will go away. Hypereosinophilic syndrome may need to be treated with prescription medicine such as corticosteroids. Health care professionals also closely watch the health of a person with this syndrome.