Why does influenza cause headache?

When influenza infects the airways, the immune system releases chemical signals to fight it. Those signals can make pain-sensitive nerves more reactive and may create an all-over unwell feeling. Fever can add to this by increasing fluid loss through sweating and making the head feel heavy or sore. A blocked or inflamed nose may also create facial pressure, especially around the forehead, cheeks, or behind the eyes. Headache is a common presentation of Influenza, but headache also has many causes outside of influenza.

Rest in a quiet, dim room and sip fluids regularly; water, soup, or an oral rehydration drink can be easier to manage when you feel ill. Eat small, simple foods if you can. A cool cloth on the forehead may feel soothing. If you can safely use an over-the-counter pain or fever medicine, follow the packet directions and check with a pharmacist if you take other medicines, have liver or kidney disease, are pregnant, or are caring for a child. Avoid giving aspirin to children or teenagers with a viral illness.

Seek urgent medical care for a sudden severe headache, a stiff neck, confusion, fainting, a seizure, trouble breathing, weakness on one side, new difficulty speaking, or a rash with fever. Arrange medical advice promptly if the headache is getting worse, you cannot keep fluids down, you have signs of dehydration such as very little urine or marked dizziness, or you are at higher risk of complications from influenza. Get advice for symptoms that do not improve as expected or that return after you had begun to feel better.

You could ask whether your symptoms fit influenza or another respiratory illness, which pain-relief options are suitable for you, and whether an antiviral medicine may be appropriate. Mention the timing of symptoms, your temperature if you have measured it, any neck stiffness, vomiting, sinus pain, medical conditions, pregnancy, and medicines you already use.