Melatonin is a hormone normally secreted by the body, affected by circadian rhythms, and has a certain relationship with sleep. The half-life of melatonin in the human body is very short, and is endogenous substances, normal consumption in accordance with medical advice is usually no obvious side effects, can be long-term, but if overdose may have the following negative effects on the body. 1, neurological symptoms: overdose of melatonin may appear dizziness, headache, drowsiness and other symptoms, but the appearance of these symptoms are mostly related to the past chaotic sleep habits, after a period of After a period of adjustment and adaptation can gradually disappear; 2, allergic reactions: some people taking melatonin will appear itchy skin, rashes and other allergic symptoms, the symptoms can be relieved after stopping the drug, if it is difficult to tolerate, you need to go to the hospital in a timely manner, under the doctor’s advice to apply local hydrocortisone cream, tretinoin acetate cream for treatment; 3, gastrointestinal symptoms: after taking melatonin may appear nausea, vomiting Abdominal pain and other symptoms, less severe symptoms do not need to stop the drug, the symptoms will gradually reduce after a period of adaptation. If the symptoms are more serious, consider suspending the use and seek medical help, you can use metoclopramide, domperidone and other drugs to relieve symptoms. In addition, when melatonin is taken for a long time and in excess, there may be side effects such as inhibiting gonadal development and promoting the release of excess lactogen in women, but this phenomenon is relatively rare. Overall, melatonin has no significant side effects and can be taken for a long period of time, which is relatively safe, but it needs to be taken strictly in accordance with medical advice and is not recommended to be taken blindly on your own. However, it is usually not necessary to take melatonin for a long time, after the sleep is regulated to normal, the body can secrete sufficient melatonin on its own, without additional supplementation.