There are many diseases that cause headache. Most headaches disappear naturally through combination of work and rest, improvement of sleep, mental relaxation or with the improvement of the treatment of the primary disease, but some headaches are signs or aura of danger. The following headaches indicate a serious condition and should be treated immediately in a hospital: 1. headache with fever; 2. headache with impaired consciousness or confusion; 3. headache with vomiting and/or blurred vision; 4. headache with limb immobility (hemiplegia, monoplegia or quadriplegia, etc.) or unusual sensations; 5. headache with significantly elevated blood pressure [blood pressure >180/120 mmHg (24/16 kPa)]; 6. Headache with double vision (diplopia); 7. Sudden and severe headache, especially if it occurs under the condition of exertion or activity, should be alerted; 8. Although headache was often present in the past, the nature of headache has recently changed or there are new accompanying symptoms; 9. Headache tends to gradually worsen after head trauma (whether or not the trauma is accompanied by bleeding from the fissure), especially if it is accompanied by vomiting; 10. There is a significant increase in headache whenever the chest and abdominal pressure increases such as coughing and stool, or there is a headache related to postural changes; 11.Sudden onset of unexplained headache in middle-aged and elderly people; 12.Headache in children with a tendency of progressive aggravation; 13.Headache complicated by pathologies of the five senses (otitis media, sinusitis, etc.); 14.Headache with epileptic-like seizures (generalized or lateral limb convulsions).