The symptoms are part of a syndrome known as Red Wine Headache, or R.W.H.

"The red wine headache is a poorly understood phenomenon," 

There are many theories about what causes the syndrome, but few facts. Dr. Fred Freitag, associate director of the Diamond Headache Clinic in Chicago, said no one really knows what leads a patient to develop this type of headache.

It may be caused by "compounds found in the skins of grapes and they are either naturally occurring or produced through fermentation," Dr. Freitag said. He would postulate no further. "It's not as if there are hundreds of thousands of dollars for funding" studies to determine the cause, Dr. Freitag said. There is actually a stigma to studying the subject.

"I've entertained the idea of looking for grants to study this and I've been told, `Don't go there, it's bad P.R.,' " Dr. Freitag said. Bad publicity comes to those who would study drinking? Carry Nation is with us yet.

Sulfites used to take the blame for R.W.H. About 20 years ago the Food and Drug Administration in America determined that about 1 percent of the population is allergic to sulfites and required that wines containing certain levels of the compound be labeled "contains sulfites." Many people have assumed, incorrectly, that the labeling is designed to warn people who get a red wine headache.

Scientists have pointed out, however, that because of their higher sugar content, many sweet white wines contain more sulfites than red wines — yet do not cause headaches in those who suffer from R.W.H. Additionally, dried fruits usually contain sulfites but you never hear of dried fruit headaches.

Sulfites can cause an allergic reaction, Dr. Freitag said, but they give headaches only to asthmatics. The more common reaction to sulfites is a breathing problem.

Other experts say that the tannins in red wine are at the root of the headaches. Tannins are the flavonoids in wine that set one's mouth to puckering. The Harvard Health Letter notes several well-controlled experiments showing that tannins in the blood cause the release of serotonin, a neurotransmitter. High levels of serotonin can cause headaches and that may happen in people who also suffer from migraine headaches.

But that does not explain why people who do not get migraines get the syndrome.

Dr. Marion Nestle, chairwoman of the department of nutrition and food studies at New York University, added that no one complains about tea, soy or chocolate headaches — though all contain tannins.

A third school of thought blames histamines. Histamines are 20 percent to 200 percent more likely to be in red wine than in white, and those who are allergic to them are deficient in a certain enzyme. Some experts believe that the combination of alcohol and that deficiency can cause the headaches. But a study of 16 people with an intolerance to wine, reported in the Journal of Allergy and Clinical Immunology in February of 2001, found no difference in reactions to low- and high-histamine wines.

For every study proving the hypothesis there is one to disprove it. Take your pick.

(One recent study suggested that prostaglandins — substances that contribute to pain and swelling — may cause R.W.H.)

Yet for most people who suffer from R.W.H., the hypotheses are irrelevant. They want to know what to do about the problem. Some Web sites suggest prevention: for histamine sensitivity, pop a nonsedating antihistamine like Claritin (or take an aspirin to stop production of prostaglandins).

Dr. Freitag frowns on this. To lick the problem, he advises what might be a long, painful and costly experiment.

Dr. Freitag, a sufferer of the headaches, said he has found he can drink some reds and not others. Almost any California red is fine but only certain reds from France — nothing in the Burgundy family, though, which includes all cabernet sauvignon grapes from Italy and Spain. But some of his patients can only drink French reds.

"If you really like red wine," Dr. Freitag said, "you should try different brands, different grapes, different countries of origin. That's the only way you are going to find out."

Here's how to challenge yourself, if you must. Drink a half a glass of red wine; if it is going to give you a headache, it will do so within 15 minutes. If there is no reaction, stick with that wine for the evening, keeping your alcohol consumption to no more than two glasses. Keep a journal.

And don't confuse R.W.H. with the headache that comes six hours after a full evening of drinking. That's called a hangover.