The hazards of anesthetics include toxic reactions and allergic reactions. 1. Toxic reaction: It is mainly manifested in symptoms of central nervous system and cardiovascular system, such as dizziness, drowsiness, polyphasia, elevated blood pressure and increased heart rate, which may even jeopardize the patient’s life. Generally, it is due to the injection of anesthetics into blood vessels, excessive dosage, rich blood supply at the injection site, or the patient’s weaker physical condition with lower tolerance. 2. Allergic reaction: allergic reaction is mainly manifested as skin urticaria and itching in mild cases, and can be manifested as pharyngeal edema in severe cases. Bronchospasm and hypotension, and may even endanger the patient’s life. An allergic reaction needs to immediately stop using drugs, first oxygen, if the effect is not good can consider using histamine or hormone drugs. Numbing drugs are usually used in hospitals by professional physicians, and basically will not produce significant harm to the human body within the safe dose range.