By Tom Nugent, Pure Matters

First, you burned breakfast. Then, you were late for work. And on your way home, the car had a flat tire, making you miss your daughter's softball game.

Now you've got this throbbing headache that has gone from a minor annoyance to a major jackhammer pounding away in your skull.

And this jackhammer crew keeps busy: An estimated 45 million Americans suffer from chronic headaches, according to the National Institute of Neurological Disorders and Stroke (NINDS) and the American College of Physicians. In fact, for half that number, that pounding pain will be severe and possibly disabling.

For most of us, though, relief is as close as the medicine cabinet: About 90 percent of all headaches are harmless episodes that can be treated with over-the-counter (OTC) painkillers—alone or together with rest, ice packs, or relaxation techniques.

Just what is a headache?

Most often, that pain is caused by one of two things:

  • An inflammation, spasm, or stretching in the scalp, in the membranes that cover the brain, and in the muscles of the face and jaw.
  • A temporary distortion of the blood vessels that supply the brain. They tighten, then relax and expand. The enlarged blood vessels press against nerves, causing pain. A shortage of serotonin, a chemical in the brain, can cause the vessels to constrict.

In general, headaches fall into three classes: tension, migraine, and cluster.

Tension headaches

The most common type of headache (accounting for about 90 percent) is the tension type. Some people describe them as a band of pressure or tightness around the head, at the back of the neck, or at the base of the skull. Some can last weeks, months -- even years.

A lot of stress factors contribute to headaches, says the National Headache Foundation. The first step in controlling chronic headache pain is pinpointing the nature of its causes and symptoms.

Migraine headaches

Unlike tension headaches, you can blame migraines on those temporary changes in the diameter of blood vessels serving the brain and scalp.

While some people call any severe headache a migraine, the real thing is usually much more intense -- throbbing pain accompanied by nausea and even vomiting. Migraines can also bring visual changes and heightened sensitivity to light, sounds, and smells.

Migraines affect more than 29.5 million Americans, who often inherit the affliction. Research has also shown ties to diet, stress, menstruation, and environmental changes.

Cluster headaches

Cluster headaches bedevil about a million Americans, mostly men and mostly at night. Like migraines, cluster headaches follow changes in the brain's blood flow. Unlike migraines, they last less than an hour and occur in predictable "clusters," three- to eight-week periods in which they can strike several times a day.

Cluster headaches produce extremely severe pain, incapacitating victims even more than migraines. But cluster headaches can enter long periods of remission.

The causes

Doctors aren't sure what causes migraines or cluster headaches, but they've identified foods and food additives that can trigger a headache.

Have you heard of "Chinese restaurant syndrome"? It's the headache some of us get after a favorite Chinese meal. It comes from the food additive monosodium glutamate (MSG), also found in some frozen foods, lunch meats, canned and dry soups, and many other processed foods.

Then there's a class of chemicals called nitrites, used to preserve bacon, sausage, canned ham, smoked fish, and other meats. Nitrites can affect the body much the same way as low levels of serotonin-blood vessels in the brain dilate, sometimes producing a headache.

And certain foods that contain tyramine, such as hard cheeses, peas, navy and lima beans, fresh bread, yogurt, alcoholic beverages, and chocolate, might trigger headaches -- especially in people who get migraines.

The NINDS recommends preventive treatment if you experience three or more headaches every month. Ditto if your headaches are increasingly unresponsive to OTC medications.