Why does the head hurt so much when infected with influenza B?

The main reason influenza B (flu B) causes headaches is due to the systemic inflammatory response triggered by the virus. Infection with the flu B virus prompts the body to produce various immune responses and release inflammatory mediators, such as cytokines and prostaglandins. These substances can affect the central nervous system, leading to blood vessel dilation and inflammation, which in turn cause headaches. Additionally, flu B often induces fever, which itself is a common cause of headaches. Dehydration or changes in sinus pressure during the course of the illness may also contribute to or worsen headaches. If headache symptoms are severe or persist, prompt medical attention is necessary to rule out other potential complications, such as encephalitis or meningitis.