The Role Eosinophils Play in Cancer

Learn what level of eosinophils indicate cancer

High levels of eosinophils can indicate cancer (e.g., colon or lung), certain infections, and other health issues. A condition known as eosinophilia, high levels are described as mild (500 to 1,500 per microliter, ml, of blood), moderate (1,500 to 5,000 per ml), or severe (5,000 or more per ml).

Eosinophils are a type of white blood cell (WBC) produced in the bone marrow. They are part of the innate immune system and can "non-specifically" destroy any invaders they encounter in the body, such as bacteria and parasites.

Woman with cancer reviews test results with doctor
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This article explains the function of eosinophils and the conditions associated with eosinophilia. It also covers what level of eosinophils indicate cancer, as well as other conditions.

The Function of Eosinophils

Eosinophils protect the body by killing bacteria and parasites. Eosinophils can circulate in the blood and also are found outside blood vessels in other organs in the body. The gastrointestinal (GI) tract typically has the highest number of eosinophils relative to other organs.

Eosinophils can cause problems when they react incorrectly and cause allergies and other inflammatory reactions in the body. For example, food allergies can cause too many eosinophils to gather in the digestive tract, which may lead to symptoms such as diarrhea and damage to the cells lining the GI tract.

When There Are Too Many Eosinophils

When a large number of eosinophils are dispatched to a certain site in the body, or when the bone marrow produces too many eosinophils, a condition known as eosinophilia exists.

Eosinophilia can result from a variety of conditions, diseases, and factors, including:

In addition, eosinophilia can develop in response to certain cancers, including:

What Level of Eosinophils Indicate Cancer?

The level of absolute eosinophils may vary based on the individual and the type of cancer they have, meaning mild, moderate, and severe levels of eosinophilia can be associated with different cancers and outcomes.

Eosinophils and Colorectal Cancer

A study published in the journal Modern Pathology looked at how eosinophils might predict outcomes for individuals with colorectal cancer. Although colorectal staging typically is based on information about the tumor itself, lymph node involvement, and the presence of metastases (cancer spread to other sites), often two individuals with the same staging will have dramatically different outcomes.

The study's authors examined whether eosinophil levels in or around a colorectal tumor helped predict outcome. They concluded that higher numbers of eosinophils around the primary colorectal tumor were associated with an improved patient outcome and, as a result, that eosinophils should be routinely counted during tumor examination.


Eosinophils are a type of white blood cell. High levels of eosinophils, or eosinophilia, can indicate cancer, fungal or parasitic infections, as well as other conditions.

While mild, moderate, and severe eosinophilia can be associated with cancer, higher levels of eosinophils around the primary tumor often predicts better outcomes in colorectal cancer.

Frequently Asked Questions

  • What level of eosinophils indicate infection?

    Levels are typically 1,000 eosinophil cells per microliter or higher in infections. In infections, levels tend to fall between moderate and severe.

  • Can high eosinophils make you tired?

    Yes, however, this will depend on the underlying cause of eosinophilia. In some cases, fatigue will not be a symptom.

  • What level of eosinophils indicate cancer in child?

    In a child with cancer, the eosinophil count may vary. In a small study, the eosinophil counts all fell in the moderate range.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Suzanne Dixon, MPH, RD
Suzanne Dixon, MPH, MS, RDN, is an award-winning registered dietitian and epidemiologist, as well as an expert in cancer prevention and management.