Headaches are a common symptom and almost all people experience headaches in their lifetime. Most headaches, which resolve quickly, have a good prognosis. Some headaches, however, are signs of serious illness and require special attention. There are many causes of headaches, and headaches are generally classified into primary and secondary headaches. The causes and mechanisms of primary headaches are not well understood, and these headaches are the most common, with recurrent attacks that seriously affect the quality of life, but the prognosis is generally good. Secondary headaches are headaches caused by other diseases. These headaches need to be taken seriously and medical attention should be sought as soon as possible to avoid delaying the diagnosis and treatment of the primary disease, which may bring serious adverse consequences. Common causes of headache: 1. Primary headache. Including migraine, tension-type headache, cluster headache, etc. 2.Secondary headache. The causes of secondary headache include intracranial diseases, diseases in the adjacent parts of the skull and brain, and systemic and somatic diseases: (1) intracranial diseases: (1) cerebrovascular diseases: cerebral hemorrhage, cerebral infarction, insufficient blood supply to the vertebral-basilar artery system, aneurysm, subarachnoid hemorrhage, venous sinus thrombosis, etc.; (2) intracranial benign and malignant tumors, parasitic cysts and granulomas; (3) inflammatory diseases: meningitis, encephalitis, cerebral abscess, etc.; (4) extracranial headaches. abscess, etc.; ④ head trauma sequelae: epidural hemorrhage, subdural hemorrhage, etc.; ⑤ other, such as hydrocephalus, etc. (2) Diseases in the vicinity of the skull: ① osteochondritis and osteomyelitis of the skull; ② glaucoma and refractive error; ③ paranasal sinusitis and nasopharyngeal carcinoma; ④ otitis media and otitis media; ⑤ pulpitis and periodontitis; ⑥ temporal arteritis; ⑦ herpes zoster of the head and face; ⑧ cervical spondylosis and frozen shoulder. (3) Systemic and somatic diseases: (1) fever caused by various reasons; (2) acute and chronic poisoning: including nitrite and sodium glutamate food poisoning, as well as carbon monoxide poisoning and acute alcohol poisoning; (3) visceral diseases: hypertension, anemia and lung, liver and kidney diseases; (4) hyperthyroidism. In short, the causes of headache are many and complex, when headache appears for the first time, or the nature of headache changes, you should seek medical attention in time to avoid delaying the disease, in addition, some chronic headache patients themselves apply a large number of painkillers for a long time, leading to drug dependence and addiction can cause harm to the body.