What causes infantile eczema (atopic dermatitis)?

Causes of Infantile Eczema (Atopic Dermatitis)

Infantile eczema (atopic dermatitis) is primarily caused by a complex interplay between genetic, immunological, and environmental factors that disrupt the skin barrier and trigger inflammatory responses. 1

Genetic Factors

• Filaggrin gene mutations play a major role in atopic dermatitis development, leading to impaired skin barrier function when deficient or absent 2
• Genetic predisposition is evidenced by family history of atopic diseases (asthma, hay fever, or eczema) being a significant risk factor 1
• Half or more of children with moderate to severe atopic dermatitis carry filaggrin mutations 2

Skin Barrier Dysfunction

• Both genetically determined barrier deficiency and environmentally caused barrier disruption contribute significantly to infantile eczema 1
• Defects in the epidermal barrier are central to the disease process, allowing increased penetration of allergens and irritants 3
• The compromised skin barrier leads to increased transepidermal water loss, resulting in the characteristic dry skin 4

Immune System Dysregulation

• Acute phase of atopic dermatitis involves significant T helper 2 (Th2) cell activation with increased expression of interleukins IL-4, IL-5, IL-13, and IL-31 1
• Chronic phase involves additional Th1 response with increased interferon-γ, IL-12, IL-5, and other inflammatory mediators 1
• Keratinocytes produce thymic stromal lymphopoietin (TSLP), IL-25, and IL-33, which activate type 2 innate lymphoid cells and induce Th2 immune responses 1

Environmental Triggers

• Environmental factors that can trigger or exacerbate infantile eczema include:
  • Exposure to allergens (particularly food allergens in early life, followed by environmental aeroallergens) 1
  • Fungal exposure (particularly significant in warm, humid climates) 1
  • Tobacco smoke exposure during pregnancy and early childhood 1
  • Air pollutants and exposure to chemicals like perfluorinated compounds and phthalates 1
  • Maternal stress and long working hours during pregnancy 1

The Itch-Scratch Cycle

• Intense pruritus (itching) leads to scratching, which damages the skin barrier further 1
• This self-perpetuating itch-scratch cycle worsens inflammation and skin barrier damage 1
• The cycle significantly impacts quality of life and can lead to sleep disturbance 4

Microbial Factors

• Altered skin structure and deficiency in antimicrobial peptides favor colonization with Staphylococcus aureus and yeasts (Malassezia sp.) 2
• S. aureus enterotoxins with superantigenic activity stimulate activation of T cells and macrophages, contributing to inflammation 2
• Changes in the skin microbiome composition can trigger or worsen atopic dermatitis 5

Clinical Implications

• Understanding these mechanisms is crucial for effective management strategies that address both barrier repair and inflammation control 3
• Early identification of risk factors may help prevent the "atopic march" - the progression from atopic dermatitis to other allergic conditions like asthma and allergic rhinitis 1
• Environmental modifications and appropriate skin care can help manage symptoms by addressing modifiable risk factors 6