Overnight milk tea is generally drinkable if it is in a sealed state, placed in the refrigerator, and observed to have not deteriorated after being taken out the next day. However, if the milk tea has been directly consumed through the mouth, or if the milk tea has been left at room temperature for too long, it is not recommended to drink it again after overnight. Because the human mouth contains bacteria, direct or indirect contact with milk tea can lead to bacteria infiltration into the milk tea. And the main component of milk tea has fresh milk, milk is rich in nutrients, creating a good environment for bacteria to survive and reproduce. It can also cause the milk tea to deteriorate because the protein in the milk is easily denatured and contaminated, which can cause abdominal pain, diarrhea and other digestive symptoms. Therefore, it is recommended to drink milk tea within a few hours after it is made on the same day, and not to leave it for too long on the same day, and the temperature should not be too high to avoid spoilage. In addition, homemade milk tea at home, although there is no preservative, but also can not prevent the reproduction and survival of pathogenic bacteria. The milk tea at room temperature is easily contaminated by bacteria, and drinking contaminated milk tea can cause food poisoning in humans in serious cases, mainly manifested as nausea, headache, followed by violent vomiting, abdominal pain, and also a small amount of yellow watery stool, which can even cause dehydration, at which time it is recommended to seek medical attention to avoid adverse consequences.