OBJECTIVE To explore the adverse reaction of neonatal hematochezia caused by vitamin AD drops and its mechanism, so as to provide reference for clinical practice.

METHODS A case of a 24-day-old female infant admitted to Shaoxing Maternity and Child Health Care Hospital in September 2024 was reported. The infant was hospitalized due to jaundice and developed hematochezia after taking vitamin AD drops; the symptom of hematochezia improved after drug withdrawal and switching to extensively hydrolyzed protein milk powder. Hematochezia recurred after changing the brand of vitamin AD drops following discharge. Diagnostic evaluation was conducted through drug withdrawal observation, stool tests, and follow-up.

RESULTS The infant developed mucous hematochezia with positive fecal occult blood test after taking two different brands of vitamin AD drops. Hematochezia was gradually relieved and disappeared after drug withdrawal, and fecal occult blood turned negative. After excluding other factors, it was determined that hematochezia was highly correlated with the highly allergenic excipients in vitamin AD drops.

CONCLUSION Vegetable oil- or animal oil-based excipients in vitamin AD drops may trigger allergic reactions in neonates, leading to hematochezia. In clinical practice, when neonatal hematochezia occurs, the medication history of supplements should be inquired, diagnostic drug withdrawal should be conducted in a timely manner, and hypoallergenic supplements are recommended for infants with hypersensitive diathesis.