March 21, 2023


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.

Medical conditions associated with increased eosinophils

Allergic Disorders

  • Asthma: A chronic inflammatory disease of the airways where eosinophils play a key role in inflammation and constriction.
  • Allergic rhinitis: Commonly known as hay fever, it is characterized by an allergic response causing itchy, watery eyes, sneezing, and other similar symptoms.
  • Atopic dermatitis: A type of eczema that is often associated with high eosinophil counts, leading to skin inflammation and itchiness.

Parasitic Infections

  • Parasitic infections, especially those caused by helminths (worms), often lead to increased eosinophil counts as these cells are important in the immune response against these organisms.

Autoimmune Diseases

  • Eosinophilic esophagitis (EoE): An inflammatory condition of the esophagus that is often considered autoimmune, where eosinophils play a central role.
  • Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome): A systemic vasculitis characterized by asthma, high eosinophil counts, and vasculitis of various organ systems.


  • Hodgkin’s Lymphoma: A type of cancer of the lymphatic system, where eosinophilia can be present.
  • Eosinophilic leukemia: A rare form of leukemia where eosinophils are produced in excessive amounts and are dysfunctional.

Skin Disorders

  • Urticaria: Also known as hives, where eosinophils can be involved in the inflammatory response.
  • Eosinophilic Folliculitis: A skin disorder characterized by itchy, inflamed bumps on the skin.

Gastrointestinal Disorders

Eosinophilic gastroenteritis: A rare condition where eosinophils accumulate in the gastrointestinal tract, causing inflammation and damage. This condition can affect any part of the gastrointestinal tract but is particularly common in the stomach.

Drug Reactions

  • DRESS syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms): A severe reaction to medications that includes eosinophilia.
  • Hypereosinophilic syndrome (HES): A group of disorders characterized by persistently high levels of eosinophils in the blood for an extended period, without a known cause, leading to damage to multiple organs.

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 reactions, infection, blood disorders including cancer, and autoimmune diseases.

What does eosinopenia mean?

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

Articles related to eosinophils on MyPathologyReport

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About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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