Understanding 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.  

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.