OBJECTIVE: To review reported cases of suspected allergic reactions to various corticosteroids. DATA SOURCES: A MEDLINE search (January 1966-December 1997) was performed to obtain case reports and review articles on allergic-type reactions to corticosteroids. Further references were obtained from these publications. STUDY SELECTION: Reports involving allergic or allergic-type reactions to systemic administration of corticosteroids were chosen for this review. An allergic-type reaction was defined as any reaction after administration of the drug that involved the appearance of adverse symptoms that are characteristic of unwanted immune responses. These symptoms include rash, sneezing, dyspnea, edema, bronchospasm, or death. Articles were excluded from the evaluation if they described reactions to topical, intraarticular, or ophthalmic corticosteroid administration. DATA SYNTHESIS: Corticosteroids are medications that are often used to treat allergic reactions. However, it appears that patients can also have allergic-type reactions to these agents. The severity of the reaction can vary from a rash to anaphylaxis or death. Both immediate and delayed reactions can occur. Allergic-type reactions are reported to occur more frequently in asthmatic and renal transplant patients than other patient populations. However, it is questionable whether all of these are true allergic responses, as there is conflicting evidence regarding the mechanism of the reaction. The most commonly implicated corticosteroids are methylprednisolone and hydrocortisone, but reactions have also occurred with others. Intradermal skin testing can help determine cross-sensitivity, although its value has not been conclusively demonstrated. CONCLUSIONS: Clinicians should be aware that allergic reactions to corticosteroids are possible. Worsening of symptoms may not always mean treatment failure, but may indicate an allergic reaction. High doses of corticosteroids (> or = 500 mg) should be given over 30-60 minutes, and patients should be observed after administration for at least the same time period. Asthmatics, renal transplant patients, and hemodynamically unstable patients may be at higher risk for adverse events. If a patient is found to be allergic to one corticosteroid, intradermal skin testing may help identify another corticosteroid that can be tolerated.