what causes a headaches
More serious causes of secondary headaches include: 1  meningitis: inflammation of the meninges which presents with fever and meningismus, or stiff neck. 2  bleeding inside the brain (intracranial hemorrhage). 3  subarachnoid hemorrhage (acute, severe headache, stiff neck WITHOUT fever).
Headache is a non-specific symptom, which means that it has many possible causes, including fatigue and sleep deprivation, stress, the effects of medications and recreational drugs, viral infections and common colds, head injury, rapid ingestion of a very cold food or beverage, dental or sinus issues, and many more.