a case-control study was carried out aiming to describe the cases and causes of anaphylaxis associated with the vaccine against measles, mumps and rubella. a total of 22 reported cases in children who showed mucocutaneous manifestations, during the campanha nacional de vacina？？o (brazilian vaccination campaign), conducted in the city of curitiba, southern brazil, in 2004, were studied. in addition, 66 children, who were next to these cases and did not show a symptomatology after the vaccine was applied, were selected. serum measurements of antibodies for vaccine antigens and total ige, specific ige antibody measurements for several allergens, and skin tests were performed. vaccine response was adequate, specific ige measurement and skin tests showed that potential allergens in vaccines and atopy were not associated with anaphylactic reactions. skin tests with the vaccine and dextran were positive in the cases exclusively, suggesting sensitization to certain residual components of the vaccine and possible cross-reaction with dextran.