Although corticosteroids have immunosuppressive, anti-inflammatory, and anti-allergic effects, allergic reactions are rare. We report a case involving a 52-year-old-female with acute urticaria caused by oral methylprednisolone. The patient had experienced aspirin-exacerbated respiratory disease (AERD) for 13 years with frequent asthma exacerbations. Symptoms of asthma exacerbations improved with short-term treatments of systemic steroids, including methylprednisolone or deflazacort, which had been well tolerated. However, the current admission was prompted by the development of acute generalized urticaria following the oral ingestion of methylprednisolone (8 mg) for relief of symptoms. An oral provocation test with 4 mg oral methylprednisolone led to generalized urticaria 20 minutes later, confirming the causal association. This is the first report of acute urticaria caused by oral methylprednisolone in a patient with AERD.