After the third injection of the new coronavirus vaccine, if the arm is swollen and itchy, i.e. local reactions such as redness, swelling, hard nodules and itching appear at the vaccination site, but there is no serious infection, the skin surface is not pus-flowing, the body temperature is in a normal state, and there are no skin lesions such as pimples, it is generally normal and can recover on its own within a few days, and patients can not worry too much. In general, patients should keep the injection site dry and pay attention to personal hygiene on the day of vaccination. And after the vaccination is finished, it is necessary to stay at the vaccination site for 30 minutes. If the symptoms of redness, swelling and itching are very serious, you can report to the local vaccination unit in time during the stay, and if it is judged that an allergic reaction has occurred, you can seek medical treatment through the vaccination site in time if necessary. If there is no abnormality after examination, it is judged to be a normal reaction to vaccination, after which it can be treated according to the normal post-vaccination process, i.e., continued observation at home after observation, which can usually be gradually relieved. In addition, after vaccination, it is still necessary to consciously comply with the requirements of vaccination prevention, to do a good job of personal protection in daily life, and to maintain good living habits such as wearing a mask, washing hands regularly, ventilating frequently, and paying attention to maintaining a safe social distance. In addition, it is important to provide the vaccination history to the receiving doctor during the consultation and treatment of the underlying disease. When there are local reactions such as redness, swelling and itching at the vaccination site, you should pay attention to your daily diet and avoid eating cold, spicy and irritating foods, such as cold drinks, hot pot, chili peppers, onions and ginger. Try to avoid drinking alcohol, smoking and other bad habits.