MUNDANE MYSTERIES: Why Does My Arm Hurt After Getting A Flu Shot?

Gotten your flu shot yet this year? If you have, good on you! If you haven’t…do it!


If you’ve ever gotten a flu shot in your life, though, your upper arm probably felt sore for a day or two. And, according to immunologists, that’s just a sign that the vaccine’s doing what it’s supposed to.


The way the influenza vaccine works, it introduces a foreign substance called an antigen into your body, which, in this case, is a deactivated/“dead” virus similar to the flu. When you expose cells in your immune system to an antigen, it “primes” them to create antibodies if/when they ever encounter that foreign substance again. Because it’s an inactive virus in the vaccine, it can’t make you sick. But, it does sensitize your immune system to potential threats. So, basically, the vaccine puts your body on high alert for anything resembling the flu, which enables you to fight off infections & illnesses faster & more effectively than without the vaccine.


When it takes on that inactive flu virus, your immune system also puts out histamines. They cause inflammation, which is important during an infection, since it helps your body fight off the bad stuff & repair damage. But, that’s also what causes soreness. The flu shot, usually injected into your upper arm, is why your body’s early immune response (and pain) tends to be concentrated there.


Around 1-in-5 people have this sort of painful reaction. But, if you tend to be sore after receiving a flu shot, there are a few things you can do to alleviate the pain. Doctors advise taking ibuprofen about 2 hours before getting the shot. Also, try putting ice on the injection site to reduce redness & swelling. Be sure to move your arm around after getting the shot, too, so the vaccine isn’t as concentrated in just the one place. Aside from that, try getting the vaccine in your non-dominant arm so any pain doesn’t interfere with your everyday activities.


Any pain is worth it, though, since odds are that you could get the flu in the future, even if you’ve never gotten the flu before. And, getting a flu shot contributes to herd immunity, as well, helping to protect those around you at higher-risk like children, older adults, and those with chronic illnesses who often can’t get the flu vaccine themselves. Keep your vaccines up-to-date! It’s an easy way to help keep your community healthy, and, with most insurances, it’s free!


Got a Mundane Mystery you’d like solved? Send me a message via social media (@AndyWebbRadioVoice), or shoot me an email at [email protected].