Eosinophilia

By Mayo Clinic staff

• Definition
• Causes
• When to see a doctor

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Definition

Eosinophilia (e-o-sin-o-PHIL-e-uh) is a higher than normal level of eosinophils, one of the five major types of disease-fighting white blood cells.

High levels of eosinophils can circulate in your blood (blood eosinophilia), but high eosinophil concentrations may also occur at the site of an infection or inflammation (tissue eosinophilia).

Tissue eosinophilia may be found in tissue samples taken during an exploratory procedure or in samples of certain fluids, such as mucus released from nasal tissues. If you have tissue eosinophilia, the level of eosinophils in your bloodstream is likely normal.

Blood eosinophilia may be detected with a blood test, usually as part of a complete blood count. A count of more than 500 eosinophils per microliter of blood is generally considered eosinophilia in adults. A count of more than 1,500 eosinophils per microliter of blood that lasts for several months is called hypereosinophilic syndrome.

Causes

Eosinophils play two roles in your immune system:

• Destroying foreign substances. Eosinophils can consume foreign substances — particularly substances related to infection with a parasite — that have been "flagged" for destruction by other components of your immune system.
• Regulating inflammation. Eosinophils help promote inflammation, which plays a beneficial role in isolating and controlling a disease site, but inflammation can also damage tissues. Immune system disorders, such as allergies, can contribute to ongoing (chronic) inflammation. Eosinophils are key players in inflammation associated with allergies and asthma.

Eosinophilia occurs when either a large number of eosinophils are recruited to a specific site in your body or bone marrow produces too many eosinophils. This can be caused by a variety of conditions, diseases and factors, including:

• Parasitic and fungal diseases
• Allergies, including to medications or food
• Adrenal conditions
• Skin disorders
• Toxins
• Autoimmune diseases
• Endocrine disorders
• Tumors

Specific diseases and conditions that can result in blood or tissue eosinophilia include:

Parasitic diseases and allergic reactions to medication are among the more common causes of eosinophilia. Hypereosinophilic syndrome tends to have an unknown cause or results from certain types of cancer, such as bone marrow or lymph node cancer.

When to see a doctor

Eosinophilia is usually found when your doctor has ordered blood tests to help diagnose a condition you're already experiencing. It's not often an unexpected finding or simply discovered by chance.

Talk to your doctor about what these results mean. Evidence of blood or tissue eosinophilia and results from other tests may indicate the cause of your illness, or your doctor may suggest other tests to assess your condition.

Because a separate condition is often the cause of eosinophilia, it's important to determine what other conditions or disorders you may have. If you get an accurate diagnosis and can treat any relevant conditions or disorders, the eosinophilia will likely resolve.

However, if you have persistent hypereosinophilic syndrome, it's important to continually work with doctors and monitor your health, as this condition may cause significant complications over time.

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