What causes eosinophils absolute to be high

What are Eosinophils?

Eosinophils are a type of white blood cell, a crucial component of the immune system. They are produced in the bone marrow and circulate in the bloodstream before migrating into tissues throughout the body. Eosinophils play a vital role in defending the body against certain types of infections, particularly those caused by parasites. They also contribute to allergic responses and can be involved in inflammation.

Understanding Absolute Eosinophil Count

The absolute eosinophil count (AEC) is a measurement of the total number of eosinophils in a cubic millimeter of blood. A normal AEC typically ranges from 0 to 500 cells per microliter (mcL) of blood. When this count exceeds the normal range, it is referred to as eosinophilia. A high eosinophil count, or eosinophilia, can indicate that the body is reacting to something, often an allergen, parasite, or an inflammatory process.

Common Causes of High Absolute Eosinophils

Allergic Reactions

Allergic reactions are the most frequent cause of elevated eosinophil counts. When the body encounters an allergen (e.g., pollen, dust mites, pet dander, certain foods, insect venom), it can trigger the release of histamine and other chemicals. Eosinophils are recruited to the site of the allergic reaction to help manage and resolve the inflammation. Conditions associated with allergic reactions that can lead to eosinophilia include:

• Allergic rhinitis (hay fever)
• Asthma (especially eosinophilic asthma)
• Eczema (atopic dermatitis)
• Food allergies
• Drug allergies
• Allergic bronchopulmonary aspergillosis (an allergic reaction to a fungus)

Parasitic Infections

Parasitic infections, particularly those caused by helminths (worms), are another significant cause of eosinophilia, especially in developing countries and tropical regions. Eosinophils are particularly effective at targeting and destroying larger parasites that are too big for phagocytes like neutrophils to engulf. Common parasitic infections that can cause high eosinophil counts include:

• Ascariasis (roundworm infection)
• Hookworm infection
• Schistosomiasis (bilharzia)
• Trichinosis (from undercooked pork)
• Strongyloidiasis

Asthma

Asthma is a chronic inflammatory disease of the airways characterized by reversible bronchoconstriction and increased mucus production. A specific subtype, known as eosinophilic asthma, is defined by the presence of elevated eosinophils in the airways or sputum. These eosinophils contribute to airway inflammation, hyperresponsiveness, and mucus plugging, leading to asthma symptoms like wheezing, shortness of breath, and coughing. In these cases, the absolute eosinophil count in the blood may also be elevated.

Skin Conditions

Certain dermatological conditions can also lead to an increase in eosinophils. These conditions often involve inflammation and immune responses in the skin. Examples include:

• Pemphigus
• Pemphigoid
• Eczema (as mentioned under allergic reactions)
• Drug reactions affecting the skin

Drug-Induced Eosinophilia

A variety of medications can cause an elevation in eosinophil counts as an adverse reaction. This is known as drug-induced eosinophilia. The mechanism can vary, but it often involves an immune-mediated response to the drug or its metabolites. Common culprits include:

• Antibiotics (e.g., penicillins, cephalosporins)
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Anticonvulsants
• Allopurinol
• Antiretroviral drugs

It's important to note that eosinophilia due to a drug may occur even after the medication has been stopped, and it can be a marker for more severe drug hypersensitivity syndromes.

Less Common Causes of High Absolute Eosinophils

Autoimmune Diseases

Some autoimmune diseases, where the immune system mistakenly attacks the body's own tissues, can be associated with eosinophilia. These include:

• Systemic lupus erythematosus (SLE)
• Rheumatoid arthritis
• Eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome), a specific vasculitis characterized by eosinophilia and granulomatous inflammation.
• Inflammatory bowel disease (Crohn's disease and ulcerative colitis)

Cancers (Malignancies)

In some instances, elevated eosinophil counts can be a sign of certain types of cancer. This is often referred to as paraneoplastic eosinophilia. Cancers that have been linked to eosinophilia include:

• Hodgkin lymphoma
• Non-Hodgkin lymphoma
• Leukemia
• Lung cancer
• Ovarian cancer
• Colorectal cancer

Other Causes

Other less common causes of eosinophilia include:

• Hypereosinophilic syndromes (HES): A group of disorders characterized by persistent and marked elevation of eosinophils in the blood and tissues, leading to organ damage.
• Certain viral infections (though less common than bacterial or parasitic)
• Addison's disease (adrenal insufficiency)
• Sarcoidosis

Diagnosis and When to See a Doctor

A high absolute eosinophil count is usually discovered incidentally during a routine complete blood count (CBC). If eosinophilia is detected, your doctor will likely conduct further tests to determine the underlying cause. This may involve a detailed medical history, physical examination, allergy testing, stool analysis for parasites, imaging studies, and potentially a bone marrow biopsy. It is important to consult a healthcare professional if you have a persistently high eosinophil count or if you experience symptoms that might indicate an underlying condition, such as unexplained rashes, persistent cough, shortness of breath, abdominal pain, or fatigue.