The Pathology Dictionary Team
March 21, 2023

What are eosinophils?

Eosinophils are a type of white blood cell (WBC) and a part of the body’s innate immune system. They help protect the body against allergens and infections. When examined under the microscope, eosinophils are small cells with bright pink cytoplasm. The cytoplasm of the cell is filled with small round granules and the nucleus has two lobes.


What do eosinophils do?

Eosinophils are designed to kill and remove micro-organisms, in particular, fungi and parasites from the body. They do this by producing and releasing chemicals that are toxic to micro-organisms.

Where are eosinophils normally found?

After being produced in the bone marrow, eosinophils travel in the blood to tissues throughout the body. The largest number of eosinophils are found in organs that contact the outside environment including the stomach, skin, and lungs. Eosinophils are often found in areas of chronic inflammation.

What does eosinophilia mean?

Eosinophilia means that there is a higher-than-normal number of eosinophils in your blood. Causes of eosinophilia include allergies, asthma, drug reaction, infection, blood disorders including cancer, and autoimmune diseases.

What does eosinopenia mean?

Eosinopenia means that there are a lower-than-normal number of eosinophils in your blood. Conditions associated with eosinopenia include Cushing’s syndrome and sepsis (severe infection).

What is an eosinophilic abscess?

A collection of eosinophils inside tissue is called an eosinophilic abscess. Eosinophilic abscesses are often seen in areas of infection, especially infections caused by fungi or parasites. If the collection is large enough, it can form a sticky substance called pus. An eosinophilic microabscess is a small group of eosinophils inside tissue. Microabscesses can only be seen when the tissue is examined under a microscope.

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