Atopic eczema
A defective skin barrier, often driven by filaggrin deficiency, lets water escape and irritants and allergens penetrate, triggering a Th2 immune response, so treatment restores the barrier first and calms the inflammation second.
In a nutshell
A leaky, often filaggrin-deficient skin barrier lets water escape and allergens in, provoking a Th2 immune response that drives itch and inflammation. Emollients repair the barrier and are foundational; topical steroids treat the resulting inflammation during flares.
Classic presentation
An itchy child or adult with dry skin and erythematous, poorly-demarcated patches in the flexures, with a personal or family history of atopy.
Key points
- The primary defect is barrier failure (often filaggrin loss-of-function), not a primarily immune disease: emollients address the root cause.
- Th2 cytokines (IL-4, IL-13, IL-31) drive itch directly, sustaining an itch-scratch cycle that further damages the barrier.
- Distribution shifts with age: face and extensors in infants, flexures in older children and adults.
- The defective barrier predisposes to Staphylococcus aureus infection and, rarely, widespread herpes simplex (eczema herpeticum), a dermatological emergency.
- Treatment is a ladder: emollients always, topical steroids for flares, calcineurin inhibitors as steroid-sparing options, then specialist systemic therapy for severe disease.
First-line investigation
None routinely: the diagnosis is clinical (itchy skin plus supporting UK diagnostic criteria). Swab if infection is suspected.
First-line management
Liberal, regular emollients as the foundation, with a topical corticosteroid added during flares to suppress the Th2-driven inflammation.
Exam traps
- Eczema herpeticum presents with monomorphic punched-out vesicles and systemic upset; it needs urgent aciclovir, not just more steroid.
- Emollients are maintenance therapy for everyone, not just an adjunct used during flares.
- Fear of topical steroids ("steroid phobia") leading to under-treatment is a common and correctable cause of poor control.
Educational content pending clinical review. Not medical advice.