Why Does it Hurt?

What hurts when you have a headache? Several areas of the head can hurt, including a network of nerves which extends over the scalp and certain nerves in the face, mouth, and throat. Also sensitive to pain, because they contain delicate nerve fibers, are the muscles of the head and blood vessels found along the surface and at the base of the brain.
The bones of the skull and tissues of the brain itself, however, never hurt, because they lack pain-sensitive nerve fibers.
The ends of these pain-sensitive nerves, called nociceptors, can be stimulated by stress, muscular tension, dilated blood vessels, and other triggers of headache. Once stimulated, a nociceptor sends a message up the length of the nerve fiber to the nerve cells in the brain, signaling that a part of the body hurts. The message is determined by the location of the nociceptor. A person who suddenly realizes "My toe hurts," is responding to nociceptors in the foot that have been stimulated by the stubbing of a toe.
A number of chemicals help transmit pain-related information to the brain. Some of these chemicals are natural painkilling proteins called endorphins, Greek for "the morphine within." One theory suggests that people who suffer from severe headache and other types of chronic pain have lower levels of endorphins than people who are generally pain free.

Headache

An estimated 45 million Americans experience chronic headaches. For at least half of these people, the problem is severe and sometimes disabling. It can also be costly: headache sufferers make over 8 million visits a year to doctor's offices. Migraine victims alone lose over 157 million workdays because of headache pain.
Understanding why headaches occur and improving headache treatment are among the research goals of the National Institute of Neurological Disorders and Stroke (NINDS). As the leading supporter of brain research in the Federal Government, the NINDS also supports and conducts studies to improve the diagnosis of headaches and to find ways to prevent them.