Adverse reactions to cow's milk in the first year of life occur in 2-7%. There is an increase in the incidence of cow's milk protein allergy (CMA) in newborn population including premature infants. We report two cases of CMA in preterm twins. The first one developed recurrent episodes of proctocolitis and the second one two necrotizing enterocolitis (NEC) -like episodes. Our cases demonstrate different clinical presentations of the same disease and add to literature the peculiarity of the early onset, the recurrence of episodes of enterocolitis associated with increasing systemic eosinophilia and episodes clinically and radiologically mimicking NEC.