Boiling expired milk is not recommended. Expired milk may contain bacteria as well as bacterial breakdown products, and boiling for a sustained period of time will kill the bacteria, so foods that have been adequately heated generally do not contain live bacteria. Some expired food is not spoiled, but since it cannot be accurately determined by taste, it is not recommended for food safety. However, expired and spoiled milk contains bacterial breakdown products and their toxins that remain in the food (e.g. sulphur-containing compounds, amines, indoles), which may cause toxic side effects such as diarrhea and fatigue when ingested by humans. Although many expired foods are heated, some people do not cause obvious symptoms after consumption, but in fact, the damage caused by the body may be relatively mild, in a hidden state. Therefore, after boiling expired milk, it is still recommended not to drink it, and the same goes for other expired foods.