There are several common clinical causes of arm pain after blood sampling: a. The patient’s failure to apply local pressure after blood sampling can cause continuous extravasation of blood down the needle hole, resulting in a large amount of local oozing of blood, manifested as skin bruising and accompanied by obvious swelling and pain. At this time, the patient needs local compression as soon as possible to avoid blood extravasation, while giving local ice to reduce tissue exudation, forty-eight hours later using hot towels wet compresses, local massage, physical therapy can promote the faster absorption of bruising and reduce the pain symptoms of the arm. Second, if the patient does not bandage and disinfect the eye of the needle after the blood is drawn, it can cause local bacterial infection and cause vasculitis resulting in painful symptoms in the arm. At this time will be accompanied by local redness and swelling, skin temperature rise, can be through 50% magnesium sulfate local wet compress to reduce the pain symptoms, oral cefixime particles to strengthen anti-infection, arm pain symptoms can be more quickly relieved.