Atopic Dermatitis

Atopic dermatitis is a chronic, relapsing inflammatory skin disease marked by intense itch and eczematous skin lesions. Type-2 inflammation, driven in part by interleukins 4 and 13, disrupts the epidermal barrier and inflames the skin. Healthy stratum corneum functions like tightly fitted mortar between bricks: it keeps water in and irritants out. In atopic dermatitis, that seal becomes leaky. Water loss dries the skin, while irritants and allergens penetrate more easily and sustain inflammation. The resulting pruritus drives scratching, which further injures the barrier. This itch-scratch cycle explains why a small flare can become widespread, excoriated, and difficult to settle. The diagnosis is clinical. Look for a history of recurrent itch with eczematous lesions and periods of improvement followed by flares. Lesions may be erythematous, scaly, excoriated, weeping, thickened from chronic scratching, or dyspigmented after inflammation resolves. In deeply pigmented skin, inflammation may appear violaceous, grey, or darker than surrounding skin rather than bright red; texture change, scale, warmth, and lichenification can be more informative than colour alone. Atopic dermatitis itself is not contagious. Secondary bacterial infection and herpes viral...