Secondary lactose intolerance may be related to viral infections or enteritis, and recovery takes about 1 to 2 months. 1. Viral infection: If it is induced by enterovirus such as norovirus or rotavirus, you need to take probiotics such as Lactobacillus and Bifidobacterium to improve the intestinal function as prescribed by the doctor, and it will usually take 4 to 6 weeks to recover. 2. Enteritis: If secondary lactose intolerance is induced by enteritis, it is necessary to actively treat the enteritis, including replenishing salt solution, taking montelukast as prescribed by the doctor, taking ibuprofen or acetaminophen; and according to the cause of the infection, taking penicillin or cephalosporin for bacterial infections, it usually takes about 2 weeks, and if the child is in poor physical condition, it may take 1 to 2 months. In addition, secondary lactose intolerance may bring some adverse effects to the child’s growth and development, parents are advised to take their children to the hospital in a timely manner, and follow the doctor’s advice to actively treat.