I just got a flu shot today and was wondering how moving your arm around helps the flu shot. I’m well aware that flu shots contain a saline solution, but where does the solution go, and how does moving your arm affect it.
In: Biology
The flu shot is a muscle injection so the shot goes into the muscle.
Something to understand about the body is that internally you are basically a slightly leaky collection of tissues. Lots of transport is done by the circulatory system yes, but you are still slowly oozing fluids around outside of the circulatory system. Most of this eventually gets picked up by the lymph system and recycled.
As for moving your arm, motion or massaging helps accelerate this oozing by shifting stuff around internally and changing pressure on things. This spreads out the fluid at the injection site faster than if you were to just let it ooze around by itself. It doesn’t necessarily help so much for the shots effectiveness, but it can spread out the injection over a larger area faster and accelerate the movement of your immune cells oozing around which can help with soreness.
A flu shot is an intramuscular injection. This means you inject the medication directly into the deltoid muscle on your arm. Moving your arm around after the injection helps with absorption. It basically just mobilizes your arm which increases blood flow which increases the rate the medicine is absorbed and circulated.
The saline solution goes into your circulatory system, distributed around the body, and gets peed out later just as if you’d drank water or ate salt.
Moving your arm around increases blood flow through the area, getting vaccine and the saline distributed into your circulatory system, and the increased blood flow also helps healing.
It also just hurts ‘cus you’re poking directly into into muscle.
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