The vaccine arm swollen a hard and itchy, can be localized hot compresses, for observation. The arm of the vaccine is swollen and itchy, if there is no obvious rash, ulceration, most of the vaccine is not fully absorbed or an allergic reaction caused by the vaccine. The main use of local hot compresses to ease the symptoms of mild allergic reactions can be observed, if the symptoms of allergic reactions are more serious, it is recommended to consult a doctor in a timely manner. If the same situation exists after the first two shots of the vaccine, there is no need to worry too much, mostly belongs to the adverse reaction after vaccination. When the vaccine stays in the local area and is not fully absorbed in time, redness, swelling and pain may occur locally. Due to the stimulation of the nerves of the surrounding tissues or the body’s allergy to the vaccine will appear slight itching, in addition to vaccination after eating or local contact with substances that can easily lead to allergies will also appear itchy symptoms. It is recommended that patients can apply hot compresses locally to accelerate local blood circulation and promote the absorption of the vaccine, which can relieve the symptoms of redness, swelling and itching. If accompanied by other parts of the skin rash, patients are advised to go to the hospital in time.