What exactly is happening in your body to make your body ache all over when you have the flu?

Inflammation!

To keep it simple, when you’re sick your body will flood itself with white blood cells. That along with increased blood flow and the typical fever result in aches and pain in your joints and muscles.

You’re essentially inflamed all over.

Your body produces proteins called Cytokines while sick. “Cytokines are a large group of proteins, peptides or glycoproteins that are secreted by specific cells of immune system. Cytokines are a category of signaling molecules that mediate and regulate immunity, inflammation and hematopoiesis.”

So long story short, it is indeed inflammation

The immune system sends white blood cells to fight off the infection. This can result in inflammation, which can leave the muscles in the body feeling achy and stiff.

When your body detects a foreign invader, it activates inflammatory reactions: redness, swelling and pain.

Also, your white blood cells (which are the soldiers of the body) will try to get rid of the said foreign invaders by “eating” them. If this doesn’t work, then the bone marrow will release and produce more white blood cells at an accelerated rate to help. This can cause your body to ache.

It’s your body’s immune system. When a foreign particle enters your body your immune system has like a security triggers that if it does trigger it will send T cells to fight it off. The fighting causes your body to show symptoms those symptoms are what the fu is.