Positive cutaneous response (Penicillin allergenic determinants (DAP) ® test). The in vivo cutaneous investigation was continued with intradermal testing, if the prick tests resulted in negative response at different dilutions. Skin tests were performed using penicillin’s main antigens, major determinants and (PPL) and minor determinant mix (MDM). Cutaneous tests were started with major determinants, the negative control was saline solution. In this case we recognized positive skin reaction to MDM at 1:100 and 1:10 dilutions, which verified the development of sensitization (patient 4).