Infectious diarrhea, including viral and bacterial infections, has mucosal damage and lactase damage in its pathogenesis, so lactase application can relieve diarrhea symptoms and zinc supplementation can promote mucosal repair. Oral rehydration can relieve the symptoms of dehydration. One of the bacterial infectious diarrhea should also be treated with effective antibiotics. In extra-intestinal infectious diarrhea, and diarrhea caused by the application of antibiotics, the intestine is dysbiosis, and probiotics should be supplemented mainly, while zinc should be supplemented to promote the recovery of mucous membrane, and lactase should be supplemented to relieve symptoms, and oral rehydration is necessary if dehydration exists. Lactase is mainly produced by the apical cells of the intestinal mucosa, and as long as there is damage to the mucosa, there will be damage to lactase.