Eczema (formally known as atopic dermatitis) and asthma are common chronic inflammatory conditions affecting millions globally. Both involve an overactive immune response and persistent inflammation, leading to frequent confusion about their classification. Many people assume these conditions are autoimmune diseases due to the nature of the body’s reaction and the treatments used. Classifying these disorders requires a clear understanding of the distinct ways the immune system can malfunction.
What Defines an Autoimmune Disease
An autoimmune disease occurs when the immune system mistakenly loses the ability to distinguish between its own healthy tissues and foreign invaders. This breakdown of self-tolerance causes the immune system to launch a targeted, destructive attack against specific, healthy cells and organs. The resulting damage is the primary pathology of the disease itself.
The immune response produces autoantibodies, proteins that specifically target the body’s own components. For example, in Type 1 diabetes, the immune system destroys insulin-producing beta cells in the pancreas. In rheumatoid arthritis, it targets the lining of the joints. Other examples include systemic lupus erythematosus and Hashimoto’s thyroiditis.
Classification of Eczema and Asthma
Eczema and asthma are not classified as autoimmune diseases because their primary pathology involves an overreaction to harmless external substances rather than an attack on self-tissue. They are categorized as chronic inflammatory conditions with an underlying predisposition to allergic reactions. This predisposition is known as atopy, the genetic tendency to develop Type I hypersensitivity reactions.
These two conditions, along with allergic rhinitis, are often grouped as the “atopic triad.” The typical progression, known as the “Atopic March,” often begins with eczema in infancy, followed by food allergies, and later, asthma and allergic rhinitis. This sequence highlights a shared, systemic allergic foundation.
The underlying issue is a hyper-sensitized immune system that overreacts to environmental allergens like pollen or dust mites. The inflammation in the skin or airways is a response to these external triggers, not an internal attack on the body’s own components.
Underlying Allergic Mechanisms
The specific biological process driving eczema and asthma is a Type I Hypersensitivity reaction, an immediate allergic response mediated by a specific class of antibody. This process is orchestrated by T-helper 2 (TH2) cells, a subset of white blood cells that promote allergic inflammation. When a genetically predisposed person is exposed to an allergen, TH2 cells activate and release cytokines, specifically Interleukin-4 (IL-4) and Interleukin-13 (IL-13).
These cytokines instruct B-cells to produce large amounts of Immunoglobulin E (IgE) antibodies. IgE antibodies then attach to mast cells, which are immune cells abundant in the skin and respiratory tract. Upon subsequent re-exposure, the IgE molecules on the mast cells cross-link, triggering the immediate release of powerful inflammatory mediators, such as histamine and leukotrienes.
In asthma, this chemical release in the airways causes bronchospasm, leading to the constriction of bronchial tubes and excessive mucus production. For eczema, the reaction in the skin leads to chronic inflammation, a compromised skin barrier, and characteristic itchy, red patches. This IgE-driven response to an external antigen is fundamentally different from the self-directed attack seen in autoimmune diseases.
Why the Conditions Are Often Confused
The confusion between allergic and autoimmune conditions arises from several significant areas of overlap in their clinical presentation and management. Both eczema and asthma are chronic conditions characterized by persistent, systemic inflammation that causes recurrent episodes, or “flares.” This ongoing inflammatory state, though triggered by different mechanisms, creates a similar impression of an immune system that is fundamentally out of balance.
Both conditions share a strong genetic component, suggesting a hereditary predisposition to immune system dysfunction. People with eczema or asthma also have an increased likelihood of developing co-existing autoimmune conditions, a relationship that suggests shared inflammatory pathways or genetic risk factors.
The greatest source of confusion comes from the treatments, as both types of disorders rely on immunomodulatory and immunosuppressive medications. Corticosteroids, for instance, are widely used to suppress the overall inflammatory response in both allergies and autoimmune diseases. Newer treatments, such as biologic drugs, are also effective in both categories by targeting specific inflammatory cytokines. The use of therapies that dampen the immune system leads to the assumption that the underlying disease mechanism must be the same.