The redness and swelling of the baby’s vaccination site may be due to adverse reactions to the vaccine or serious allergies or infections, which need to be identified by parents in a timely manner. 1. Adverse reactions: After vaccination, the skin may have a slight inflammation or allergic reaction, with redness, swelling, pain or even low fever, which is normal and generally does not need to be treated, and can disappear on its own after 2-3 days. For more serious pain, dry ice wrapped in a towel or cold water bag can be used to lightly compress the affected area to relieve swelling and pain, paying attention to the temperature not to be too low and the cold compress time not to be too long to avoid frostbite. Rapid allergic reaction occurs within 24 hours after vaccination and can result in erythema and papular rash with itching all over the body, and serious cases may have shock, which should be treated with antihistamines or glucocorticoids in time. The other is delayed metaplasia, which usually occurs 2-3 days after vaccination, with erythema and papules at the injection site, accompanied by itching and vesicular ooze, etc., and systemic autosensitivity dermatitis may appear on this basis, which can be treated locally with topical glucocorticoid cream, and which requires systemic antihistamines or even glucocorticoids for the whole body; 3. If the redness does not go away for a long time, the skin temperature increases significantly, touching the fluctuating sensation, etc., you need to pay attention to whether infection has occurred, the injection site contact with unclean things, such as bath water, dirty hands, etc. can cause, the child more fever, crying, depression, loss of appetite, etc., high fever can also lead to convulsions, should promptly go to the hospital to identify the infecting bacteria, targeted selection of antibiotic sterilization treatment, symptomatic available ibuprofen to reduce fever, diazepam can relieve convulsions. In general, when babies receive vaccinations, they need to be observed in the hospital for about half an hour after vaccination before leaving to avoid serious allergic reactions. You should not take a bath for 24 hours after the vaccination. If there is sweating, you can take a towel to wipe the sweating area and avoid the injection site. It is also necessary to replenish water in time to accelerate the metabolism of the baby’s body, which can largely reduce adverse reactions.