Acute urticaria is a frequent benign disease in children and is often secondary to infections. Usually it is a self-limited histamine-dependent cutaneous condition marked by
transient, erythematous, and pruritic wheals and frequently by acral angioedema. A haemorrhagic pattern characterised by annular and polycyclic lesions with central ecchymosis
is a possible presentation especially in young children and it can be so alarming as to cause hospital admission. Establishing the correct diagnosis of acute annular urticaria (a
morphologic subtype of simple infectious urticaria recently referred as urticaria multiforme) is important to prevent an unnecessary diagnostic work up. In an otherwise well-appearing child erythema multiforme, serum sickness-like reaction and acute haemorrhagic oedema of infancy are the principal differential diagnoses. A direct history and physical examination can reliably distinguish all these conditions, avoiding laboratory investigations and allowing appropriate treatment. Reassurance and oral non-sedating antihistamine
therapy are sufficient
