Patients who ingest spoiled milk may develop diarrhea, which mainly manifests as digestive symptoms. Milk spoilage contributes to a bacterial contamination that may cause abdominal pain, bloating and diarrhea in patients with bacterial enteritis. Yogurt formed by the effect of lactic acid bacteria can be left for several days without deterioration, but milk left for too long can easily breed other harmful bacteria. Lactobacillus, also known as probiotics, milk is a good medium for bacteria, which can easily make harmful bacteria multiply, and harmful bacteria multiplication can lead to milk spoilage. The human body ingests spoiled milk, which may cause the digestive tract to be involved, and the bacteria multiply within the milk and then to the intestines. Patients may have digestive symptoms, such as diarrhea, abdominal pain, and bloating, and need to go to the hospital, where doctors give patients certain medication support, medication, and fluid therapy before they may gradually get better.