Hypersensitivity to corticosteroids is a classical but rarely reported event. We report a 30-year-old patient who developed generalized urticaria after her first methylprednisolone bolus. We reviewed the relevant literature to look for factors associated with hypersensitivity to corticosteroids. Causality should be evaluated on a case-by-case basis using diagnostic criteria for drug hypersensitivity reaction. Etiopathogenesis may involve either an IgE-mediated immunoallergic reaction or semi-delayed hypersensitivity. The main problems are identification of the offending agent and evaluation of the safety of further corticosteroid therapy. Although a few fatal reactions have been reported, some were probably due to underlying cardiovascular disease or serum electrolyte abnormalities.