Eosinophils are a type of white blood cell. They help fight off infections and play a role in your body’s immune response. They can also build up and cause inflammation.
Normally your blood doesn’t have a large number of eosinophils. Your body may produce more of them in response to
Parasitic and fungal infections
Bone marrow disorders
In some conditions, the eosinophils can move outside the bloodstream and build up in organs and tissues. Treatment of the problem depends on the cause.
Causes of Eosinophilia
Eosinophils play two roles in your immune system:
Destroying foreign substances. Eosinophils can consume foreign substances. For example, they fight substances related to parasitic infection that have been flagged for destruction by your immune system.
Regulating inflammation. Eosinophils help promote inflammation, which plays a beneficial role in isolating and controlling a disease site. But sometimes inflammation may be greater than is necessary, which can lead to troublesome symptoms or even tissue damage. For example, eosinophils play a key role in the symptoms of asthma and allergies, such as hay fever. Other immune system disorders also can contribute to ongoing (chronic) inflammation.
Eosinophilia occurs when a large number of eosinophils are recruited to a specific site in your body or when the bone marrow produces too many eosinophils. This can be caused by a variety of factors, including:
Parasitic and fungal diseases
Allergies including allergies to medications or food
Specific diseases and conditions that can result in blood or tissue eosinophilia include:
Acute myelogenous leukemia (AML)
Ascariasis (a roundworm infection)
Atopic dermatitis (eczema)
Idiopathic hypereosinophilic syndrome (HES), an extremely high eosinophil count of unknown origin
Lymphatic filariasis (a parasitic infection)
Trichinosis (a roundworm infection)
Parasitic diseases and allergic reactions to medication are among the more common causes of eosinophilia. Hypereosinophila that causes organ damage is called hypereosinophilic syndrome. This syndrome tends to have an unknown cause or results from certain types of cancer, such as bone marrow or lymph node cancer.
Treatment for Eosinophilia
Treatment is based on cessation of exposure to any identified underlying condition, or to any drug or supplement. In many cases, no primary cause is found, suggesting that eosinophilia is secondary to allergy or parasitosis. In such cases, a brief trial of low-dose corticosteroids often lowers the eosinophil count, confirming the secondary nature of the raised eosinophil count.