Very rare cases of hypersensitivity reactions to various constituents of parenteral nutrition (PN) have been reported in children. Adverse effects associated with PN administration have centered on metabolic, infectious, and mechanical complications. Here we describe three cases of hypersensitivity to components of PN. Case 1 is a 1-mo-old breastfed baby with a diagnosis of acute gastroenteritis associated with an infection with cytomegalovirus. On the second day of PN, 60 min after the initiation of the infusion, the patient had an allergic reaction with an overall diffused rash. On day 4 of PN, the multivitamin solution and the trace element mix were excluded, showing a good tolerance. Case 2 is a 4-y-old girl with a background of stage III neuroblastoma. On day 3 of PN, 15 min after the initiation of the infusion, the patient showed sudden facial edema. On day 5, suspecting the amino acid solution to be the etiology of her reaction, PN was infused with another amino acid preparation, and the patient showed good tolerance. Case 3 is a 10-y-old boy with a diagnosis of an acute peritonitis. Two h after the initiation of the infusion, the patient showed a general wheal rash. He referred a background of fish allergy. Considering that the lipid emulsion used had components from fish oil (SMOF Lipid), a new PN was infused on day 2. The new PN contained a lipid emulsion containing vegetable oil (ClinOleic). The patient showed good tolerance. In conclusion, we consider that, although the hypersensitivity to PN components is infrequent, there is an increase in reports of pediatric cases describing this allergic pathology.