Eczema, formally known as atopic dermatitis, is a chronic inflammatory skin condition characterized by an impaired skin barrier and a hyper-responsive immune system. White blood cells (leukocytes) are the primary components of the body’s immune defense, and an elevated count (leukocytosis) often reflects inflammation or infection. This article addresses how atopic dermatitis and its potential complications affect systemic white blood cell levels.
The Immune Response in Chronic Eczema
Chronic atopic dermatitis is driven by Type 2 inflammation. This long-term, non-infectious inflammation causes a constant, low-grade activation of the systemic immune system, which can result in a mild, sustained elevation of the total white blood cell count.
This increase is primarily attributable to Eosinophils, leading to eosinophilia. Eosinophils are specialized white blood cells strongly associated with allergic responses, a hallmark of atopic diseases like eczema, asthma, and hay fever. The severity of the eczema often correlates with the degree of peripheral blood eosinophilia.
T-helper 2 (Th2) lymphocytes drive this allergic cascade. These cells release signaling proteins, such as Interleukin-5 (IL-5), which stimulate the bone marrow to produce more Eosinophils and direct them to the skin. Thus, the mild leukocytosis seen in chronic eczema reflects this underlying, systemic allergic inflammation.
Leukocytosis Caused by Secondary Infection
While chronic eczema can cause a mild white blood cell elevation, the most significant and acute spikes in the total count are caused by secondary infections. The compromised skin barrier in atopic dermatitis, characterized by cracks and open lesions from scratching, provides an easy entry point for microbes. This significantly increases the risk of acute infection.
The most common bacterium to colonize and infect eczematous skin is Staphylococcus aureus. When this or another pathogen breaches the skin barrier, the body mounts a massive, acute immune response that differs from the chronic allergic inflammation. This acute bacterial infection triggers a rapid and substantial increase in a different type of white blood cell, the Neutrophil.
This sharp rise in Neutrophils (neutrophilia) is a typical reaction to bacterial invasion and drives a significantly high total white blood cell count. Acute leukocytosis often signals an urgent need for medical intervention, such as antibiotics, to clear the infection.
Understanding the White Blood Cell Differential
Medical professionals use a diagnostic tool called the white blood cell differential count to interpret the source of any leukocytosis in a patient with eczema. The differential count measures the percentage and absolute number of the five major types of white blood cells: Neutrophils, Lymphocytes, Eosinophils, Monocytes, and Basophils. Analyzing this breakdown is far more informative than simply looking at the total count.
If a patient with eczema has an elevated total white blood cell count, the differential points toward the cause. A high Eosinophil percentage strongly suggests that the elevation is due to the chronic atopic or allergic inflammation inherent to the eczema itself. Conversely, a sharp increase in the Neutrophil count is a strong indicator of an acute bacterial infection complicating the eczema.
Analyzing the differential is crucial for guiding treatment. It allows clinicians to distinguish between the patient’s baseline chronic inflammatory state and an acute infection. This directs whether the patient requires ongoing management of the skin condition or immediate treatment for an infection.