There is no maximum number of days that you can drink the root of blueberry, usually according to the patient’s condition as well as the physical condition of the decision, it is recommended to follow the doctor’s instructions to use the drug. The root is the dried root of woad, a cruciferous plant. It is bitter in taste, cold in nature, and belongs to the heart and stomach meridians, with the effect of clearing heat and removing toxins, cooling the blood and facilitating the pharynx. It is used in the treatment of fever and pharyngitis, fever and sore throat, mumps, rotting throat and gua sha, big head plague, dan yu (acute infection with reddening of the skin like paint), carbuncle and swollen skin. The adverse effects and contraindications of the drug are not known. If there is a need for medication, it is recommended that it be used under the guidance of a professional physician, not blindly self-medication.