The redness, swelling, hardness, itching and burning of the arm after vaccination is due to the occurrence of an adverse reaction to the vaccine. After vaccination arm red swelling hard lumps itchy and hot situation is very normal, is the normal vaccination after the local reaction, in the vaccination before and vaccination, medical personnel will repeatedly informed of this kind of situation. The redness, swelling, hardness and itching of the arm after vaccination is due to the fact that the active ingredients of the vaccine as well as the excipients are heterologous substances, which can stimulate the immune system to produce an immune response after entering the human body. When there is redness, swelling, hard lumps and itching on the arm, you can use an ice pack to relieve the localized redness, swelling and itching and reduce discomfort. After more than 24 hours, no longer use ice packs, but switch to hot packs, hot packs can relieve the hard lumps after vaccination and assist in their gradual dissipation. But be careful to avoid getting water on the needle eye, which can easily cause infection and aggravate the local redness, swelling and pain. In addition to adverse reactions to vaccines, there may also be localized allergies or infections at the site of vaccination, for example, the patient may be allergic to the rubber gloves of the medical staff for vaccination, or bacteria enter the body through the needle wound after vaccination and cause infection, resulting in redness, swelling, hardness and itching. These are usually mild cases, so there is no need to worry about them and they can be relieved in a few days. If there is still discomfort after the above treatment, it is recommended to consult a doctor and follow the doctor’s instructions to avoid aggravation of the condition.