It is harmful to the body. Mold will be produced after the oil expires. After eating it, it may cause gastrointestinal discomfort and cause sudden diarrhea. We must improve the bad habits in our daily life. As a habit, don’t eat high-fat or high-cholesterol foods, eat regularly, have three regular meals a day, and drink plenty of boiled water, which can promote the excretion of metabolic products.

If edible oil is stored for a long time, especially the residual crude oil, which contains a lot of plant residues, the oil may become rancid. Cooking oil contains a linoleic acid component that easily reacts chemically with oxygen in the air. This phenomenon is called "fat oxidation."

A series of reactions such as oil and hydrolysis can generate oxides, peroxides and other decomposition products such as small-molecule aldehydes, ketones and carboxylic acids with special odors. The smell is caused by the oxidation and rancidity of oils. result. After the oil becomes rancid, it becomes smoky and choking when heated. It contains decomposed products such as epoxy propionaldehyde, which can easily lead to poisoning after consumption.