What Causes Eczema?
The cause of eczema (atopic dermatitis) is complex and not fully understood. Research has demonstrated a strong genetic influence in the development of this skin disease, which arises from the interplay of multiple genes with external environmental factors.
There is growing evidence to support the longstanding theory that eczema is caused by a genetic defect in the epidermis (the outermost layer of skin), permitting environmental irritants, microbes and allergens to penetrate and eliciting inflammatory responses.
- The filaggrin gene contributes to the formation and function of the skin.
- Deviations in the gene coding for filaggrin can cause skin barrier defects that contribute to eczema.
- Defects in skin barrier development prevent adequate levels of antimicrobial peptides to form in the epidermis. Consequently, bacterial (especially Staphylococcus aureus) and viral infections are common in affected lesions.
Eczema is a culmination of genetic and environmental factors that results in reduced skin barrier function and increased transepidermal water loss (water loss from within the body through the skin), which causes the persistent symptoms of dryness, itching and inflammation. Furthermore, an impaired epidermal barrier makes the skin more susceptible to hypersensitivity reactions that are caused by irritants and allergens, such as detergents, fragrances, synthetic or rough fabrics, certain foods, and dust mites.
Eczema is most common during childhood; the majority of eczema patients seem to outgrow the condition by adulthood. Coping with the physical and emotional aspects of eczema can significantly impact the quality of life of affected individuals, especially children and their caregivers.
Therefore, effective management through medical treatments, avoiding triggering factors, and practicing routine skin care are central to limiting the severity of symptoms and reducing the frequency of flare-ups.
Changes in the Body that Contribute to Eczema
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- The serum IgE levels are elevated. IgE are immunoglobulins (proteins) that are present in the skin and mucous membranes. IgE is produced in response to antigens or allergens and their levels can be measured and used as a marker of allergic-type conditions. These proteins function as antibodies in the immune system to identify and neutralize allergens. Several genes have been associated with increased production of IgE. These levels are often related to the severity of the eczema. However, 20% of individuals with atopic eczema have normal or low IgE levels.
- Neutrophils and monocytes are white blood cells that are triggered by the body's immune system to arrive at a site of infection through a process known as chemotaxis, In eczema, there is a reduction in the cell-mediated immune response. Consequently, chemotaxis of neutrophils and monocytes is reduced. These effects explain the increased risk of microbial skin infections in eczematous individuals.
- T cell activity increases in response to exposure to various antigens. The cells that are at the center of the inflammation are called T lymphocytes (T cells). T-lymphocytes are a type of white blood cell involved in regulating the body's immune responses against diseased or infected cells. They can be thought of as the soldiers of the immune system.
- The excessive stimulation of T cells in turn increases the production of IL-4 (interleukin 4). Interleukins are signalling molecules that are produced by white blood cells in order to stimulate and regulate the immune system. Elevation of IL-4 and IL-13 may inhibit the adequate formation of antimicrobial peptides, thus allowing proliferation and colonization by Staphylococcus aureus and other infectious agents on and within the skin's surface.
- There is an increase in Langerhans cells in the epidermis, causing over stimulation of T cells and the body's immune reactions. Langerhans cells reside in the epidermis and are responsible for warning the immune system if skin pathogens are present.
- An impaired epidermal barrier defense system increases water loss through the skin, which leads to subsequent dryness, itching and irritation.