Headaches are sometimes a symptom of a disease or disorder. However, most occur independently of any other disorder, and are brought on by strain on muscular tissues or temporary changes in the blood vessels of the head and neck. The severity and frequency of your pain, as well as the conditions which accompany your headache, may help determine whether you need to see a doctor. In general, you should seek medical advice if you've recently had a head injury and you've been vomiting or feel nauseated; it's painful to bend your head forward; or light hurts your eyes. Other possible danger signs are fever, dizziness, unusual sleepiness, and loss of vision or hearing. A headache that occurs alone and disappears overnight is probably no cause for concern. If you have headaches that sometimes last for more than 24 hours, or that recur as often as two or three times each week, consult a health care provider.