Why Does the Flu Cause Body Aches?   

Why Does the Flu Cause Body Aches?

Young woman sick on the couch, wrapped up in a blanket, shivering from the flu and body aches.

December 06, 2022

Clinical Contributors to this story:
John Mosko, M.D.

Does the flu make you feel so achy you just want to sleep? This is your immune system’s response to the virus.

“Flu-like symptoms, like fatigue and joint or muscle aches, are caused by inflammation,” explains family medicine physician, John Mosko, D.O. “A healthy immune system that encounters the flu or other viruses can cause these symptoms to manifest. Feeling run-down, achy, or fatigued is a good sign your body is fighting an infection.”

What the Flu Does to Your Body

One of the hallmarks of the flu is the discomfort that it causes. People who get sick may experience:

  • Fever
  • Sore throat
  • Headache
  • Joint aches
  • Muscle aches
  • Muscle inflammation
  • Muscle weakness
  • Fatigue
  • Shivering

Why the Flu Makes You Feel Achy

Having the flu or another infection launches your immune system into action. Although your immune system helps you get better, it causes you to feel worse due to inflammation. Here’s how:

  • White blood cells are key players in the immune system’s fight against infection. They travel throughout the body and help to protect you from invaders.
  • When white blood cells perceive an invader, such as the flu virus, they attack. Certain white blood cells produce antibodies that fight against viral infections.
  • These antibodies attach themselves to the virus, which prevents the virus from spreading further. This action destroys the virus over time, restoring your health.
  • When antibodies interact with a virus, it can cause inflammation in the body. This may lead to muscle aches and other discomfort that you associate with being sick.
  • White blood cells may congregate in the lymph nodes when you’re fighting infection. When this happens, the lymph nodes may appear swollen or sore.

You may associate swollen lymph nodes with having an illness. It’s an outward sign that your body is fighting back against the flu.

Your immune system is complex enough to fight off infections it has encountered before. Its past experience with certain viruses makes it easier to recover when they reappear.

Ways to Feel Less Achy When You Have the Flu

There’s no instant fix for the flu; you have to wait to feel better. But there are things you can do to be less miserable as you recuperate.

To ease the aches and pains of the flu:

  • Get some rest. Sleep helps you bolster your immune system and reserve your strength. Nap during the day, if you can.
  • Stay hydrated. Drinking water, tea, chicken broth or other liquids can counteract fluid loss. Being well-hydrated is key for helping your body ward off infection.
  • Take a warm shower. A warm shower or bath may soothe achy muscles or joints without overheating you. Opt for warm water, not hot.
  • Use NSAIDs for pain relief. Non-steroidal anti-inflammatory drugs (NSAIDs) reduce inflammation and relieve pain.

Another key way to feel less achy from the flu is to get the flu vaccine. People who are vaccinated who get the flu have milder cases than unvaccinated people.

Fortunately, the body aches that accompany the flu are temporary. Once you recover, your symptoms should fade away.

Next Steps & Resources:

The material provided through HealthU is intended to be used as general information only and should not replace the advice of your physician. Always consult your physician for individual care.


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