Phenytoin is used for the treatment and prevention of fits. We investigated all patients reported to have phenytoin allergy in our hospital and found 42 confirmed cases. Sixty-nine percent were female and 83.3% were Chinese. The mean age of the patients was 46.5 years. The reactions reported were maculopapular rash (71.4%), Stevens-Johnson syndrome (14.3%), fever (4.8%), generalized exfoliative dermatitis (2.4%), toxic epidermal necrolysis (2.4%), vasculitis (2.4%) and agranulocytosis (2.4%). In conclusion, the majority of reported allergic reactions to phenytoin were cutaneous (92.9%) and one fifth of these were potentially life-threatening.