“…The pathogenesis of Wells’ syndrome is unknown, but the currently accepted theory involves a local hypersensitivity reaction to an inciting agent. Triggers include insect bites, medications, immunizations, hematologic disorders, infections, and association with solid tumors (2,4); however, half of all patients lack a known trigger (3), as was the case in our patient. The differential diagnoses include drug reaction, bacterial cellulitis, Churg–Strauss syndrome, idiopathic hypereosinophilic syndrome, and bullous pemphigoid.…”