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

Inflammation not only affects the blood vessels but also nerves in the body, making them more sensitive to pain. This increased sensitivity can intensify and make muscle and joint aches feel more uncomfortable. The combination of inflammation and increased nerve sensitivity is what makes the flu feel so achy and miserable.

Understanding how inflammation contributes to flu symptoms can help explain why over-the-counter pain relievers that reduce inflammation can provide relief from some discomfort. Additionally, this knowledge can inform the development of new treatments for the flu that specifically target the inflammatory response itself.