Corticosteroids are potent anti-inflammatory and anti-allergic agents used in the treatment of various inflammatory diseases, including allergic disease. They are frequently considered the therapy-of-choice for many skin diseases. However, allergic reactions caused by corticosteroids have been reported. Among these, delayed reactions to topical steroids are more common, whereas immediate reactions to systemic steroids are rare. Herein, we report the case of a 32-year-old woman with triamcinolone-induced immediate hypersensitivity reaction, in which the patient had a positive prick test result with triamcinolone. She has had atopic dermatitis (AD) for three years. She had used systemic steroid, cyclosporine, and antihistamine with topical steroids for AD. In clinic, approximately 10 minutes after intralesional injection of triamcinolone, she complained of erythematous patches with slight elevation and itching on the face, trunk, and both hands. After intravenous injection of dexamethasone, her symptoms got worse. After treatment with epinephrine, all symptoms resolved within two hours. We performed an open test and skin prick test. She had a positive result only from the prick test with triamcinolone; all other steroids showed negative results from the open tests. Dermatologists should be aware of the possibility of anaphylaxis or other allergic hypersensitivity in response to corticosteroids.