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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Because its an inflammation. When you get an active vaccine, you recieve parts of a virus/bacteria which your body recognizes as an enemy and starts to fight. This leads to inflammation as immune cells swarm the affected area. Which is why vaccines typically lead to warm and sore areas for a few days.
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