After buttock injection, some people will have hard lumps and obvious pain at the injection site. There are various reasons for this situation, which are related to the depth of the injection site, and also have obvious correlation with the stimulation of the drug and individual differences. In the past, deep intramuscular injections of penicillin were often used. If the injection site is superficial, the absorption rate of penicillin is slower, and a local hard lump and pain may form, and the more times and the longer the injection, the more obvious this situation will be. In addition, there is also a relationship with the stimulation of certain drugs, and also with individual differences, such as intramuscular injection of anti-tuberculosis vaccine, some people have no obvious reaction after intramuscular injection, while some people will have obvious local redness, swelling, pain, and even fever after intramuscular injection, in this case there is a clear correlation with individual differences.