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  • You've probably gotten a lot of shots in your lifetime

  • the ones you probably freaked out over as a baby, all the way up to your last flu vaccine.

  • Either way, you might remember some shots being nastier than others.

  • Like, some aren't that bad at all, hardly more than a pinch.

  • But others hurt like no one's business, and can make your arm sore for days afterward.

  • In general, a little pain after a shot isn't a bad thing.

  • It just means your body is learning to recognize and fight off a pathogen, like the flu virus,

  • so that you don't get really sick if it shows up again.

  • But it doesn't mean that the pain is, well, any less of a pain.

  • How much a shot hurts depends on a lot of things, including where you get jabbed,

  • what's in the vaccine, and of course, your personal feeling about needles.

  • You might think that a bigger needle and a deeper shot would hurt more.

  • But in most cases, those deeper injections into muscle, or what doctors call intramuscular shots,

  • actually pose less of a problem than the ones given just under the skin.

  • Scientists aren't totally sure why this is, but they think part of it has to do with the way that each tissue absorbs fluid.

  • If you inject a bunch of fluid into fatty skin, it doesn't have much of a place to go and can get trapped,

  • which can be painful.

  • Muscles, meanwhile, are full of blood vessels and can clear out the liquid much more quickly,

  • so they tend to cause less pain, swelling, and redness.

  • As a bonus, muscles also tend to have a better mix of immune cells,

  • so intramuscular shots are often more effective.

  • Besides where the shot is given, how much a shot hurts also depends on what's in it.

  • Some vaccines contain adjuvants,

  • which are materials added to vaccines to make it easier for your immune system to recognize the pathogen you want to avoid.

  • They're inflammatory, and made of things like aluminum, or small parts of bacteria.

  • They're harmless, but since they aren't normally found in your body,

  • adjuvants cause more immune cells to come to the scene of the injection to check out what's there,

  • and to begin processing it.

  • It turns out that some of the more painful vaccines,

  • including those that protect against tetanus or the human papillomavirus, also called HPV, tend to have adjuvants in them.

  • And in the case of HPV, the version of the vaccine that patients report as being more painful actually has two adjuvants in it.

  • If that sounds terrible, remember, they're there because they make the vaccine work better.

  • In fact, so far, it looks like the double-adjuvant vaccine might help people have stronger and longer-lasting protection.

  • Scientists are still working on making vaccines less painful, but for now, it's no pain, no gain, as they say.

  • Although, of course, if you have severe pain after a shot, or if it's lasting a long time,

  • you should consult your doctor.

  • We are definitely no substitute for professional medical advice.

  • SciShow is produced by Complexly,

  • a group of people who believe the more we understand, the better we get at being human.

  • If you want to learn more about vaccines, shots, or anything else related to healthcare,

  • you can go check out one of our other channels, Healthcare Triage, over at




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Why Do Some Shots Make Your Arm Hurt So Much?

  • 6 1
    joey joey に公開 2021 年 06 月 04 日