Alum is a traditional food additive, but alum contains aluminum ions, and alum is consumed, basically can not be discharged from the body, it will always be deposited in the body, so there are chronic toxic side effects. Its toxic side effects are mainly manifested in alum can kill brain cells, so that people early brain atrophy, dementia and other symptoms, affecting people's intelligence, the impact on life is not significant.　　At the same time, if people in their daily life after excessive consumption of aluminum, it will affect the absorption of iron, calcium and so on, leading to osteoporosis, anemia, affecting the development of nerve cells.　　Alum is a traditional water purifier and has been widely used. But in recent years, alum has rarely been used as a purifying agent, mainly because the aluminum contained in alum is harmful to the human body. Long-term consumption of alum-purified water may cause Alzheimer's disease.　　Alum is used as an adsorbent in the production of hair masks, and should not be used in excess; prolonged overdose can lead to chronic poisoning.　　Alum crystals in the air will have some volatilization, but will not have any harm to the human body.　　Tips: Alum is sometimes used to pass off as crystal. Alum crystals and crystals are extremely similar, but because of the hardness of the two are different, alum crystals will be slightly dissolved in water, the solution is milky white, and there will be crystals off.