Lactose intolerance in children primarily causes an imbalance in the gut microbiome, leading to digestive system symptoms such as bloating, diarrhea, and abdominal pain. The main mechanism is the insufficient secretion of lactase in the baby's intestines, which fails to digest and absorb lactose in food, resulting in symptoms of lactose intolerance. In such cases, the intake of probiotics orally and reducing the intake of foods containing lactose can be helpful. If the baby is fed with formula or breast milk, taking lactase orally or switching to lactose-free formula milk for feeding can be considered. If the child has already started on solid foods, halt the intake of dairy products and simply continue feeding with solid foods, such as porridge, noodles, or rice flour. If a baby shows signs of lactose intolerance, it is crucial to monitor for symptoms of dehydration. If there are signs like poor skin turgor, low energy, or reduced urine output, it is essential to seek medical attention promptly from a specialist to manage and prevent the aggravation of dehydration symptoms.