Diarrhea in children after drinking formula milk stems from various causes. Most often, these include lactose intolerance, cow's milk protein allergy, an immature digestive system, gut microbial imbalance, or issues with milk preparation or quality. A change from breast milk to formula, or switching formula types, can also trigger digestive upset and diarrhea as the child's system adapts.

For a two-year-old with three days of diarrhea after drinking formula, the cause is more likely related to intolerance or incompatibility with the milk rather than a bacterial infection. Bacterial contamination usually presents with rapid onset symptoms after consumption. A child might experience frequent vomiting, fever, severe abdominal cramps, continuous diarrhea, and signs of dehydration like intense thirst, dry lips, reduced urination, and lethargy. Parents must seek prompt medical attention for their child in these situations for timely assessment and treatment.

Conversely, if a child's diarrhea occurs while drinking milk but improves after cessation, temporary lactose intolerance may be the cause. Following a digestive upset, the child's intestinal lactase enzyme temporarily diminishes, impairing lactose absorption from milk. This results in diarrhea, bloating, abdominal distension, and sour-smelling stools. Cow's milk protein allergy is also a notable cause, though it is more prevalent in younger infants. Symptoms can include prolonged diarrhea, skin rashes, fussiness, spitting up, and stools containing mucus or traces of blood.

Master, Doctor, Level I Specialist Trinh Thi Hong Van, Pediatrics Department, Tam Anh General Hospital TP HCM, examines a child with a digestive disorder. *Photo: Trung Vu*

Parents can manage this by temporarily switching to a more suitable milk, such as low-lactose or lactose-free options, or hydrolyzed milk. They must ensure correct milk preparation ratios, sterilize utensils, and store milk according to instructions. Additionally, parents should supplement with probiotics, offer easily digestible foods, and monitor for any unusual signs.

If a child's diarrhea persists, accompanied by frequent vomiting, dehydration, or bloody stools, parents must seek medical evaluation for appropriate assessment and treatment. Parents should take their child to the hospital if diarrhea lasts over 5-7 days, if stool contains blood or mucus, if the child experiences weight loss, or shows signs of dehydration (intense thirst, dry lips, reduced urination, fatigue).

Parents must select products with clear origins, purchase from reputable establishments, and check packaging, expiration dates, and seals. Avoid frequently changing milk formulas in a short period, as this can prevent the child's digestive system from adapting, easily leading to recurrent diarrhea.

Master, Doctor Le Thi Hong Hue

Pediatrics Unit, Tam Anh General Clinic District 7