A headache is probably the most common symptom to be experienced by mankind, and may be associated with problems of any of the multiple complex structures in the head, or disorders of many of the body’s other organs. Fatigue, stress and anxiety may in themselves cause it, or may trigger muscle spasms in the temples and scalp that are responsible for the pain.
Any infection, by a bacteria (eg. tonsillitis, sinusitis, ear infection, bronchitis, urinary infection), virus (eg. influenza, common cold, glandular fever, hepatitis), fungus or parasite (eg. malaria), may cause a headache, as may a fever of any cause.
Injury to any part of the head may cause one, but sometimes, and very seriously, the headache may occur some days after the injury due to slow bleeding from a leaking vein within the skull.