Alum, also known as alum, is a refined product of alum stone, the chemical name is potassium aluminum sulfate. Alum is not only used as a chemical raw material, but also used for water purification. Alum is cold, sour and astringent, with a strong astringent effect, Chinese medicine believes that alum has detoxification and insecticide, dry dampness and itching, stopping bleeding and diarrhea, clearing heat and eliminating the effects of phlegm. In addition, alum is also a traditional food improver and bulking agent, commonly used as an additive in the production of doughnuts, vermicelli, rice noodles and other foods. However, because the chemical composition of alum is potassium aluminum sulfate, containing aluminum ions, so excessive intake will affect the body's absorption of iron, calcium and other ingredients, leading to osteoporosis, anemia, and even affect the development of nerve cells. Therefore, some nutrition experts propose to eat as little food containing alum as possible. There is no hard and fast rule on the dosage of alum, because it varies according to the needs of various products, but alum contains a lot of aluminum, because the regulations only make provisions for the residual amount of aluminum. According to the national hygiene standard of food additives, the maximum use of alum is "according to the production needs of the appropriate amount of use", but the residual amount of aluminum should be ≤ 100mg/kg. Alum contains aluminum, so it has a great toxicity. Aluminum itself is very easy to accumulate in the human body, such as in the brain, kidney, liver, spleen and other organs may produce accumulation, if the brain to produce deposition is easy to cause Alzheimer's disease, memory loss, mental decline and other symptoms!