When the influenza virus enters the body, it triggers an immune response that leads to inflammation. This inflammation causes blood vessels to become leaky, allowing immune cells to travel to the site of infection and attack the virus. However, this process also results in characteristic flu symptoms such as muscle and joint aches.

Inflammation can also affect nerves in the body, causing them to become more sensitive to pain. This increased sensitivity can make the muscle and joint aches feel more intense and uncomfortable. The combination of inflammation and heightened nerve sensitivity is what makes the flu so achy and miserable.

Understanding the role of inflammation in flu symptoms can help explain why over-the-counter pain relievers that reduce inflammation can alleviate some discomfort. Additionally, this knowledge can inform the development of new treatments for the flu that target the inflammatory response itself. By reducing inflammation, these treatments may be able to provide relief from some of the most common symptoms associated with influenza.