Causes of Eczema (Atopic Dermatitis)
Eczema results from a complex interaction between genetic skin barrier defects (particularly filaggrin gene mutations), immune system dysregulation, and environmental triggers—not from a single isolated cause. 1
Genetic and Hereditary Factors
Approximately 70% of atopic dermatitis patients have a family history of atopic disease, making family history one of the two most consistently and strongly associated risk factors. 1
Loss-of-function mutations in the filaggrin (FLG) gene represent the second major genetic risk factor, causing impaired skin barrier function through increased trans-epidermal water loss, pH alterations, and dehydration. 1, 2
These genetic defects in the epidermal barrier are now recognized as central to disease predisposition and perpetuation, representing a paradigm shift in understanding atopic disease. 3
Immune Dysregulation
An imbalance toward Th2-mediated immune responses creates alterations in cell-mediated immunity and promotes IgE-mediated hypersensitivity, both playing critical roles in disease development. 2, 4
This immune dysfunction is central to atopic inflammation and has proven to be a powerful target for biological therapy. 3
Environmental Triggers and Exacerbating Factors
Early Life and Allergen Exposures
Food allergens represent the major allergic triggers in early life (particularly cow's milk, eggs, wheat, soy, and peanut in young children), after which environmental aeroallergens become critical. 1, 5
Aeroallergens (house dust mites, pollens, animal dander, and fungi) affect both occurrence and severity of disease, especially in moderate to severe cases. 1, 5
In humid climates like Taiwan, fungi represent a major risk factor among aeroallergens. 1
Chemical and Environmental Exposures
Tobacco smoke exposure during pregnancy and early childhood is associated with increased risk of developing atopic dermatitis. 1
Exposure to perfluorinated chemicals and phthalates is positively correlated with elevated serum IgE levels and disease development. 1
Environmental pollutants, airborne formaldehyde, harsh detergents, fragrances, and preservatives can trigger responses from both innate and adaptive immune pathways. 2
Maternal and Prenatal Factors
- Elevated maternal work stress and long working hours during pregnancy increase the risk of atopic dermatitis in young children. 1
Physical and Lifestyle Factors
Soaps and detergents strip natural lipids from already compromised skin, worsening dryness and barrier dysfunction. 1, 5
Extremes of temperature and irritant fabrics (such as wool) exacerbate symptoms. 1
Use of harsh alkaline detergents in skin care products unfavorably alters the skin's pH, causing downstream changes in enzyme activity and triggering inflammation. 2
Infectious Triggers
Bacterial colonization/infection, particularly Staphylococcus aureus, causes disease deterioration with crusting and weeping. 1, 5
Grouped, punched-out erosions indicate herpes simplex infection as a trigger for flares. 5
Geographic and Climate Factors
- Patients living in humid climates or developing countries may manifest atopic dermatitis only after changing locale or following onset of respiratory allergies. 1
Common Pitfall to Avoid
- The development and phenotypic expression depend on complex interactions between genetic factors, environmental allergen exposure, and nonspecific adjuvant factors such as pollution, infections, and climate—clinicians must avoid attributing the disease to a single cause and instead recognize this multifactorial nature. 1