What causes hand eczema in a child, considering atopic background and environmental irritants?

What Causes Hand Eczema in Children

Hand eczema in children results from a complex interplay between genetic skin barrier defects, immune dysregulation, and environmental triggers—with atopic dermatitis being the single most important causative factor, followed by allergic contact dermatitis and exposure to irritants. 1, 2

Primary Causative Mechanisms

Genetic and Barrier Dysfunction

• Filaggrin gene mutations are among the strongest genetic risk factors, impairing formation of the stratum corneum and leading to earlier onset and more severe disease 1
• Approximately 70% of children with eczema have a positive family history of atopic conditions (eczema, asthma, or allergic rhinitis), with risk increasing 2-3× with one atopic parent and 3-5× when both parents are affected 1
• The skin barrier defect allows increased penetration of allergens, irritants, and microbes, triggering inflammatory cascades that create a self-perpetuating itch-scratch cycle 1, 2

Immune System Dysregulation

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

Specific Causes by Classification

Atopic Hand Eczema (Most Common)

• Atopic dermatitis is the definitive diagnosis in approximately 36% of children with hand eczema referred for evaluation 3
• Atopic dermatitis and wet work are the two most important risk factors for developing hand eczema 4, 5
• Children with atopic background have inherent barrier dysfunction that makes hands particularly vulnerable to environmental triggers 6

Allergic Contact Dermatitis (Second Most Common)

• Allergic contact dermatitis accounts for approximately 33% of hand eczema cases in children 3
• The most frequent allergens detected in children are thiomersal (21%), nickel (12%), mercury (12%), and cobalt (10%) 3
• The pattern and morphology of hand dermatitis is unreliable in distinguishing atopic from allergic contact dermatitis, making patch testing essential 7

Irritant Contact Dermatitis

• Exposure to primary skin irritants including water (frequent hand washing), harsh soaps containing emulsifiers/surfactants that damage the skin barrier 7
• Irritant contact dermatitis is less common than allergic contact dermatitis in children but carries a better prognosis once irritants are identified and avoided 7

Environmental Triggers and Aggravating Factors

Specific Environmental Exposures

• Fungal exposure is a major risk factor, particularly in warm and humid climates 7
• Tobacco smoke exposure during pregnancy and early childhood increases risk 7
• Air pollutants may increase prevalence and severity 7
• Maternal work stress and long working hours during pregnancy increase risk in young children 7

Occupational and Recreational Factors

• Exposure to specific products during activities such as painting, decorating, recreation, or sport 7
• Contact with vegetables (potato, garlic), meats, fish, flour, or animal dander in food handlers or those helping with cooking 7

Critical Clinical Pitfalls to Avoid

Common Diagnostic Errors

• Do not assume the pattern or morphology of hand dermatitis can distinguish between atopic, irritant, or allergic causes—this is unreliable even in experienced hands 7
• Any child with hand eczema in whom an allergic cause is suspected should be referred for patch testing, as allergic contact dermatitis manifesting as hand eczema is not uncommon 3
• Deterioration in previously stable hand eczema may indicate secondary bacterial infection (look for crusting/weeping) or development of contact dermatitis 7, 8

Management Misconceptions

• Dietary restriction is of little or no benefit in most cases and should only be attempted in selected infants under professional supervision to avoid nutritional deficiencies 7, 1
• Attempts to eradicate house dust mites are not currently recommended as evidence does not support this intervention 7, 1
• Introducing solid foods at any particular age, or avoiding allergenic foods during infancy, does not modify the risk of developing eczema 1
• Breastfeeding for six months is recommended for general health benefits but does not prevent eczema 1

Red Flags Requiring Urgent Evaluation

• Grouped, punched-out erosions or vesiculation indicate herpes simplex infection (eczema herpeticum), requiring immediate systemic acyclovir and viral culture 7, 8
• Crusting or weeping lesions suggest Staphylococcus aureus superinfection, requiring swabs for culture and consideration of flucloxacillin 7, 8

Practical Assessment Algorithm

Initial History Must Include

1. Personal history of atopic dermatitis in infancy or childhood, plus other atopic features (asthma, hay fever) and family history of atopy 7
2. Where symptoms began initially and where they spread later 7
3. Relationship to application of any particular product (cosmetics, personal-care products, topical medications, clothing, gloves) 7
4. Detailed history of all wash products, as most contain harsh emulsifiers/surfactants that damage the skin barrier in predisposed individuals 7
5. Relationship to specific activities (hairdressing, holidays, home improvements, recreation, sport) 7
6. Whether symptoms improve when environment changes (weekends, holidays) and recur on return to specific settings 7

Physical Examination Focus

• Extent, location, and severity of eczema 7
• Presence of crusting, weeping (bacterial infection), or punched-out erosions (viral infection) 7, 8
• General dry skin (xerosis) supporting atopic diagnosis 8
• Age-specific distribution: cheeks/forehead in children under 4 years versus flexural involvement in older children 8