Atopic dermatitis, commonly known as eczema, is a long-term inflammatory skin condition affecting millions globally. A healthcare provider often checks the white blood cell (WBC) count as a general measure of immune system activity during routine blood tests. Eczema can cause a high total white blood cell count, a finding that reflects the body’s ongoing inflammatory state.
Eczema as a Chronic Inflammatory Condition
Eczema is fundamentally an immune system disorder, not merely a condition of dry skin. The underlying pathology involves a hyper-responsive immune system reacting to environmental triggers, leading to chronic inflammation. This immune response is primarily driven by Type 2 inflammation, a pathway associated with allergic and atopic diseases like asthma and hay fever.
A significant contributing factor is dysfunction in the skin barrier, often linked to genetic mutations in the filaggrin protein. A deficiency creates a “leaky” barrier that allows allergens and irritants to easily penetrate the skin, activating immune cells in the deeper layers. This activation triggers a cycle where immune cells release chemical signals, necessitating a sustained, systemic immune reaction that influences the white blood cell population circulating in the bloodstream.
The Direct Link to Elevated White Blood Cell Counts
Eczema can directly lead to an elevated total white blood cell count, a condition medically termed leukocytosis. This increase is specific to the cells involved in allergic and atopic responses, primarily driven by an increase in a specific subtype of white blood cell: Eosinophils.
Eosinophils are characteristic cells of Type 2 inflammation. Their numbers often increase in the bloodstream and migrate to the skin to combat the perceived allergic threat. Immune cells release Interleukin-5 (IL-5), a signaling molecule that promotes the production and movement of eosinophils. High eosinophil levels, known as eosinophilia, are a common finding in individuals with eczema and can correlate with the severity of the disease itself.
Lymphocytes may also be affected, though their presence in the blood can be variable. While some studies show higher total lymphocyte counts, in severe cases, lymphocytes may move out of the circulating blood and into the inflamed skin tissue (lymphopenia). The overall elevated white blood cell count in chronic eczema reflects the body’s persistent, Type 2-skewed immune activity in response to the skin barrier breach.
Differentiating Chronic Inflammation Markers from Acute Infection
When a complete blood count shows an elevated total white blood cell count, the first concern is often an acute bacterial infection. However, a high count caused by chronic eczema presents a distinct profile, which can be distinguished by looking at the white blood cell differential—a breakdown of the percentages of each cell type.
In uncomplicated, chronic eczema, the elevated total count is primarily due to the increase in Eosinophils and potentially Lymphocytes, as these cells manage the allergic inflammation. In contrast, an acute, systemic bacterial infection, such as a skin infection like impetigo or cellulitis, is characterized by a significant spike in Neutrophils. An acute infection causes a condition called neutrophilia, where the body rapidly produces and releases neutrophils to fight the invading bacteria.
If a person with eczema develops a secondary bacterial skin infection, their white blood cell profile will dramatically shift. The blood test will show not only the chronic elevation of eosinophils but also a substantial, acute rise in neutrophils. This shift is a crucial indicator for healthcare providers, often accompanied by the presence of immature neutrophils, known as a “left shift,” which signals a rapid and robust response to a bacterial threat. Therefore, interpreting the differential count is essential to correctly distinguish the chronic inflammatory marker of eczema from the acute infectious marker.