Dermatitis herpetiformis is the intensely itchy skin condition associated with coeliac disease — sometimes called Duhring’s disease. It appears as clusters of small blisters and bumps, typically on the elbows, knees, buttocks, and scalp, and the itching is famously fierce, often worse at night. The cause is the same gluten-driven autoimmunity as coeliac disease: IgA antibodies deposited in the skin trigger the eruption, and most patients show the intestinal damage of coeliac disease on biopsy even without gut symptoms. Diagnosis is confirmed by skin biopsy, and the cornerstone of treatment is the same strict gluten-free diet — the rash fades over months as gluten leaves the system, though the drug dapsone can suppress the itching faster. For dietitians it is coeliac disease wearing a dermatological disguise.