Why do shots (i.e. flu, tetanus) hurt for a few days after receiving them?
In: Biology
Many injections, including tetanus and some flu vaccines, are administered intramuscularly- that is, into a large muscle. This is favored because it allows fast absorption of the injection, and has some other advantages over other types of injection.
However, at the micro level, you’re punching a needle through sensitive, innervated muscle tissue. This causes trauma to the muscle and associated pain until the damage is repaired.
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