Why did my penicillin shot become red around the injection area?

Redness around the injection site after a penicillin shot can occur due to a localized reaction, which might be a normal response of the body to the medication. It may also indicate irritation from the injection itself or an allergic reaction. If the redness is accompanied by swelling, pain, or persists for an extended period, it's advisable to consult a healthcare professional for further evaluation.