When you get sick, your immune system goes into overdrive to fight off the infection. In fact, part of this response involves releasing antibodies, which is a natural response to infection or injury and is intended to help your body eliminate the virus, according to Loma Linda University Health. However, this response by the immune is what causes body aches in the first place.
At this point, your body also produces more white blood cells, which are a key part of our immune system — they help produce cytokines. Cytokines are small proteins produced in response to various stimuli, including infections, injuries, and inflammation, per the Cleveland Clinic. They play a crucial role in the body’s immune response to infection and coordinate the communication and activity of different cells in the immune system. However, the increased cytokine production triggers an inflammatory response and causes muscle and joint pain, which eventually leads to those dreaded body aches.