Arm pain after vaccination is usually a general reaction caused by the vaccine, which is caused by the vaccine components stimulating the muscles and nerves. Patients with more severe pain and symptoms such as local redness, swelling and fever may also be caused by allergic reactions and local infections, which require symptomatic treatment. Common causes and treatments 1. Allergic reactions: Some patients may have allergic reactions such as arm pain, itching, papules and blisters after vaccination, and patients whose symptoms do not subside may go to the hospital for clear diagnosis and corresponding treatment. Patients who have been diagnosed with allergic reactions should also pay attention not to use drugs without authorization to prevent the reaction between vaccine components and anti-allergic drugs, which may cause more serious adverse reactions; 2. Local infection: Some patients may have secondary bacterial infections due to improper care of the injection site, which may produce symptoms of infection such as arm pain, redness and swelling, or even local pus. After a clear diagnosis by the doctor, the patient can follow the doctor’s prescription to apply topical erythromycin ointment, mupirocin ointment and other drugs to promote the fading of infection symptoms and relieve pain. After vaccination, patients should pay attention to a light diet and avoid intake of spicy and stimulating foods to avoid local vasodilatation, which increases the permeability of blood vessels and results in increased local exudation, causing edema and pain. In addition, it should be noted that no bath should be taken within 24 hours, and no local redness, swelling and exudation should be taken only after 24 hours, otherwise, secondary infection will easily occur.