Lactic acid is not harmful to the human body, it can only cause local muscle soreness, but it does not cause other substantial lesions, so patients do not need to worry too much. The main cause of lactic acid is that the patient participates in heavy physical labor or sports, which leads to anaerobic muscle exercise and lactic acid, and then the accumulation of lactic acid can cause local muscle soreness. The soreness can be improved by applying heat to the area and kneading it appropriately. When the lactic acid is metabolized, the soreness will be relieved on its own. So lactic acid does not have much effect on the human body, and when it is metabolized, the soreness in the body will subside on its own.