Eczema (Atopic Dermatitis)
Overview
Atopic dermatitis (AD, eczema) is a chronic, relapsing inflammatory skin condition characterised by intense pruritus, dry skin and eczematous inflammation. It commonly begins in infancy or childhood but often persists into adulthood.
AD is associated with a personal or family history of atopy (asthma, allergic rhinitis) and frequently shows elevated IgE and sensitisation to environmental, food or microbial antigens. The disease causes significant sleep disturbance, psychosocial morbidity and reduced quality of life (NICE CG57).
Pathophysiology AD results from interacting genetic, barrier and immune abnormalities:
- Skin barrier defect, often linked to filaggrin loss‑of‑function and altered epidermal lipids, leading to increased transepidermal water loss and greater allergen/irritant penetration.
- Immune dysregulation with Th2 predominance in acute disease (IL‑4, IL‑13 driving increased IgE) and mixed Th1/Th22 responses in chronic lesions.
- Common Staphylococcus aureus colonisation that amplifies inflammation; viral superinfection (herpes simplex) may cause eczema herpeticum.
- The “atopic march”: infantile AD often precedes allergic rhinitis and asthma.
Clinical features
- The hallmark symptom is pruritus; itch often predates visible eruption.
- Morphology: erythematous papules and vesicles with oozing in acute flares; dry, scaly, excoriated and lichenified plaques in chronic disease.
- Typical distribution by age:
- Infants: face (cheeks), scalp, trunk and extensor surfaces; the diaper area is usually spared.