What causes eczema in infants?

Causes of Eczema in Infants

Infantile eczema results from a complex interplay between genetic predisposition, skin barrier dysfunction, immune system dysregulation, and environmental triggers—with family history of atopic disease being the strongest predictor. 1

Genetic Factors

Family history is the most significant risk factor for infantile eczema. Children with a mother who has eczema face nearly 3-fold increased risk (OR 2.80), while paternal allergic rhinitis increases risk by approximately 2-fold (OR 1.91). 2 The heritability of eczema is substantial, estimated at 73.59% when considering parental history. 3

• Filaggrin gene mutations are a key genetic contributor, increasing eczema risk more than 3-fold (OR 3.20). 2 These mutations cause genetically determined skin barrier deficiency. 1
• Specific genetic variants in CD14-159C/T and IL4Ralpha I75V genes significantly increase susceptibility, particularly when both are present together (OR 3.44). 4

Skin Barrier Dysfunction

The skin barrier defect is central to infantile eczema pathophysiology, occurring through both genetic and environmental mechanisms. 1

• Barrier disruption allows increased penetration of allergens, irritants, and microbes, triggering inflammatory cascades. 1
• This creates a self-perpetuating itch-scratch cycle where scratching further damages the barrier, worsening inflammation and pruritus. 1

Immune System Dysregulation

The infant immune system in eczema shows characteristic Th2-dominant inflammation. 1

• Acute phase: Marked by T helper 2 (Th2) cell activation with elevated IL-4, IL-5, IL-13, and IL-31. 1
• Chronic phase: Additional Th1 response develops with increased interferon-γ and IL-12. 1
• Keratinocytes produce thymic stromal lymphopoietin (TSLP), IL-25, and IL-33, which activate type 2 innate lymphoid cells and amplify Th2 responses. 1

Environmental Risk Factors

Perinatal and Birth Factors

• Prematurity and low birth weight significantly increase eczema risk. 3
• Shorter birth length is protective—each centimeter increase in birth length reduces risk (OR 0.87 per cm). 2

Early Life Exposures

• Antibiotic use before age 1 year substantially increases eczema risk. 3
• Humid living environment during pregnancy and the infant's first year is a significant risk factor. 3
• Exposure to allergens, fungal elements, tobacco smoke, and air pollutants can trigger or exacerbate disease. 1
• Maternal stress during pregnancy may contribute to eczema development. 1

Protective Factors

• Dog ownership in the home reduces eczema risk by approximately 50% (OR 0.44-0.54), particularly when exposure occurs during the first year of life. 4, 2 This protective effect is most pronounced in children carrying the CD14-159C/T CC genotype. 4

Clinical Implications

Understanding these causes is critical because eczema often represents the first step in the "atopic march"—the progression from atopic dermatitis to asthma and allergic rhinitis. 1, 5 Early identification of high-risk infants (those with family history of atopy, filaggrin mutations, or multiple environmental exposures) may enable preventive interventions.

Common Pitfalls

• Do not assume all cases have identifiable triggers—the multifactorial nature means some infants develop eczema despite minimal environmental exposures. 6
• Avoid recommending dietary restrictions without professional supervision, as evidence shows little benefit in most cases and risks nutritional deficiency. 6
• Do not attempt house dust mite eradication as a preventive measure—current evidence does not support this intervention. 6