What is Eosinophilia?

Eosinophilia is having high levels of eosinophils, which are a type of immune cell that is normally present in the blood and certain tissues, including the spleen, lymph nodes and thymus and parts of the gastrointestinal, respiratory and genitourinary tracts.

When the body wants to attack a substance, such as an allergy-triggering food or airborne allergen or a parasite, eosinophils respond by moving into the area and releasing a variety of toxins. (Read more: What is an Eosinophil?) However, when the body produces too many eosinophils, called “eosinophilia”, the eosinophils can cause chronic inflammation resulting in tissue damage. 

How Many Eosinophils is Too Many? 

What are “normal” or “above-normal” amounts of eosinophils? Currently, there are no published, established guidelines to answer this question, and the amount of eosinophils will vary by location in the body. However, we know from our clinical laboratory here at Cincinnati Children’s that the maximum absolute eosinophil count (AEC) in the peripheral blood varies by age, with it being higher in younger children.  

Maximum Absolute Eosinophil Count (AEC) in Peripheral Blood chart.

What Could Too Many Eosinophils Be From?

Eosinophilia can be caused by short-term infections temporarily increasing eosinophil levels. Eosinophilia can also be caused by many disorders in which the number of eosinophils has been found to be increased in the blood or in different tissues. 

Importantly, eosinophilic gastrointestinal disorders (EGIDs), rare conditions in which eosinophilia occurs in one or more segments of the gastrointestinal tract, can be difficult to diagnose due to the lack of established “normal” values of eosinophils in the blood and tissues and to the many possible acute and chronic conditions that have eosinophilia as a symptom. (Read More: What is an Eosinophilic Disorder?)

General categories of disease, each with examples of those that have increased levels of eosinophils, are presented below. These conditions range from allergic disorders to endocrine disorders. As these are all possible diagnoses for a patient with eosinophilia, physicians must use additional information to determine the right diagnosis for an individual patient. 

Allergic disorders are classically characterized by the presence of eosinophils. Allergic rhinoconjunctivitis (hay fever) has increased levels of eosinophils in the nasal mucosa. Asthma, after an exacerbation, shows increased numbers of eosinophils in the lung and blood. Atopic dermatitis (aka, eczema) has increased levels of eosinophils in the skin and peripheral blood. Eosinophilic gastrointestinal disorders have increased levels of eosinophils in portions of the gastrointestinal tract (esophagus, stomach, small intestine, large intestine, or multiple segments).

Any drug / medicine (prescription, non-prescription, supplements) has the potential to cause a reaction. Some of these reactions are allergic in nature, and eosinophils might be elevated in blood or in tissues where the drug is concentrated.

Connective tissue and inflammatory disorders, including eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome), rheumatoid arthritis, sarcoidosis and inflammatory bowel disease can have increased eosinophil levels.

Parasitic infections, fungal infections and some other types of infections are associated with increased numbers of eosinophils. Below are presented different types of infection and specific infectious organisms or conditions.

  • Helminth (especially tissue-invasive)
  • Ectoparasite (scabies, myiasis)
  • Fungi (especially coccidiomycosis and allergic bronchopulmonary aspergillosis [ABPA]

Eosinophilia is rarely associated with infections by protozoa (except for Sarcocystis and Isospora belli) or by bacteria (except for resolving scarlet fever and tuberculosis [TB]) or by viruses (except for advanced HIV).

Hematologic, neoplasm and myeloproliferative disorders with increased levels of eosinophils include hypereosinophilic syndrome, leukemias (myelogenous and lymphocytic), lymphomas (especially Hodgkin lymphoma, cutaneous T cell lymphoma [CTCL] and other T cell lymphomas), tumors (e.g., adenocarcinoma of the bowel, lung, ovary or other solid organ), myeloproliferative neoplasms (e.g., PDGFRA-, PDGFRB- or FGFR1-associated), systemic mastocytosis and atheroembolic disease (e.g., cholesterol embolism syndrome).

Immunodeficiency (especially DOCK8 deficiency, STAT3 deficiency [e.g., hyper-IgE syndrome] and Omenn syndrome), thymomas, and transplant rejections are only a few types of immunologic conditions with increased numbers of eosinophils.

Hypoadrenalism has been associated with increases in the levels of eosinophils in the blood.

Eosinophilia Clinic

The Division of Allergy and Immunology hosts a specialized Eosinophilia Clinic for patients with peripheral blood and / or tissue eosinophilia and eosinophilic conditions.

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What is an Eosinophilic Disorder?

Eosinophilic disorders occur when eosinophils are found in above-normal amounts in various parts of the body.

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