What Causes Eczema on Baby's Skin
Baby eczema (atopic dermatitis) is caused by a combination of genetic skin barrier defects and immune system dysfunction, with family history of atopic disease and filaggrin gene mutations being the two strongest and most consistent risk factors. 1
Primary Genetic Causes
Family history is the most powerful predictor: Approximately 70% of babies with eczema have a positive family history of atopic diseases (eczema, asthma, or hay fever). 1 The risk increases 2-3 fold with one atopic parent and 3-5 fold if both parents have atopic disease, with maternal history being particularly predictive. 1
Filaggrin gene mutations are the second major cause: Loss-of-function mutations in the FLG gene disrupt the skin's protective barrier by preventing normal formation of the stratum corneum. 1 These mutations lead to earlier-onset disease, more severe symptoms, and more persistent eczema. 1 However, not all babies with eczema have filaggrin mutations, and conversely, about 40% of individuals with these mutations never develop eczema—demonstrating that genetics alone don't tell the whole story. 1
Skin Barrier Dysfunction Mechanism
The disrupted skin barrier is central to disease development through both genetic and environmental pathways. 2, 3 When the barrier is compromised, allergens, irritants, and microbes penetrate more easily, triggering inflammatory cascades. 3 This creates a vicious itch-scratch cycle where scratching further damages the barrier, worsening both inflammation and itching. 2, 3
Immune System Dysregulation
The baby's immune system shows characteristic abnormal responses: 3
- Acute phase: Dominated by T helper 2 (Th2) cells producing IL-4, IL-5, IL-13, and IL-31, which worsen barrier dysfunction and drive itching. 2, 4
- Chronic phase: Additional Th1 response develops with increased interferon-γ and IL-12. 2, 4
- Keratinocyte activation: Skin cells produce thymic stromal lymphopoietin (TSLP), IL-25, and IL-33, which amplify the allergic immune response. 2, 3
Environmental Triggers
While not primary causes, environmental factors can trigger or worsen eczema in genetically susceptible babies: 2, 3
- Exposure to allergens, fungal elements, tobacco smoke, and air pollutants 2, 3
- Maternal stress during pregnancy 2, 3
- Urban living appears to increase risk, though specific causative agents remain unclear 1
- Black race increases risk independent of other factors 1
Important Clinical Pitfalls to Avoid
Do not recommend dietary restrictions without evidence: The timing of solid food introduction or withholding allergenic foods does not alter eczema risk. 1 Most dietary modifications show no protective effect, and indiscriminate food allergy testing leads to false positives and harmful unnecessary dietary restrictions. 5 Breastfeeding for 6 months is encouraged for other benefits, not eczema prevention. 1
Do not recommend house dust mite avoidance as prevention: Despite babies with eczema often being sensitized to dust mites, there is no strong evidence that dust mite avoidance strategies prevent atopic dermatitis. 1, 3
Recognize this is often the first step in the "atopic march": Understanding these causes is critical because infantile eczema frequently progresses to asthma and allergic rhinitis later in childhood. 2, 3
Birth factors have minimal impact: Cesarean versus vaginal delivery does not alter eczema risk, and the effect of birth weight is likely negligible despite conflicting studies. 1