Diarrhea in infants is a common clinical disease in pediatrics. The loss of nutrients and intestinal dysfunction in the body during diarrhea make it very easy for various complications to occur and affect the healthy growth of infants. Disruption of fluid balance is an important condition for maintaining normal physiological functions. Since infants are relatively immature in fluid regulation, disorders of water-electrolyte and acid-base balance are more likely to occur during diarrhea. Fluid imbalance is very dangerous and should be detected and corrected in time. Dehydration is the most frequent fluid imbalance. In severe cases, electrolytes are lost along with body fluids, the most common one being hypokalemia. Hypokalemia is the most common cause of hypokalemia. Hypokalemia can induce muscle weakness, cardiac arrhythmias and renal impairment. Metabolic acidosis is also a complication of severe diarrhea, caused by the loss of large amounts of alkaline substances due to diarrhea and the accumulation of acids in the body with impaired acid excretion. Infants may show symptoms such as depression, deep and rapid breathing and exhalation of acetone-smelling gas [1]. Malnutrition can result from prolonged or chronic diarrhea. In addition to the loss of a large amount of nutrients during diarrhea, long-term diarrhea can disrupt the normal digestive and absorption internal environment of the infant’s intestine, resulting in impaired nutrient absorption, thus causing malnutrition, which in turn causes atrophy and degeneration of the gastrointestinal mucosa, further affecting the digestion and absorption of nutrients, forming a vicious cycle. Therefore, the cause of diarrhea should be actively searched for and treated, and diet should be adjusted to ensure sufficient calories and nutrients. Diarrhea in infants is one of the main contributing factors to the development of intestinal entrapment. Diarrhea causes disturbances in intestinal peristalsis, and low potassium causes a decrease in intestinal smooth muscle dynamics, especially in viral diarrhea, which can cause edema and congestion in the intestinal wall, ileal lymph node hyperplasia and local intestinal wall thickening, leading to the occurrence of intussusception [2]. Intussusception is a life-threatening emergency, and clinicians should be highly alert and perform ultrasound to diagnose it clearly if they find sudden crying, irritability, abdominal distention, and vomiting in children with diarrhea. Secondary lactose intolerance in infants with diarrhea, especially rotavirus-infected diarrhea, can cause destruction of the intestinal mucosa, resulting in secondary lactose intolerance, which in turn can aggravate diarrhea, leading to a vicious cycle of prolonged diarrhea. Lactose deprivation diet is important for the treatment of secondary lactose intolerance. Studies have shown [3] that lactose-free formula with other treatments significantly reduced diarrheal symptoms and shortened the duration of diarrhea (2.436 days vs. 3.762 days, t=8.1953, P<0.001).