"A headache (cephalalgia in medical terminology) is a condition of pain in the head; sometimes neck or upper back pain may also be interpreted as a headache. It ranks amongst the most common local pain complaints and may be frequent for many people.

The vast majority of headaches are benign and self-limiting. Common causes are tension, migraine, eye strain, dehydration, low blood sugar, and sinusitis. Much rarer are headaches due to life-threatening conditions such as meningitis, encephalitis, cerebral aneurysms, extremely high blood pressure, and brain tumors. When the headache occurs in conjunction with a head injury the cause is usually quite evident. A large percentage of headaches among women are caused by ever-fluctuating estrogen during menstrual years. This can occur prior to, or even during midcycle menstruation.