As the holiday season kicks off this week, many will be making a consequential choice at dinner: red wine or white wine? And if your choice is red, will you be risking a headache? The fact that red wine can sometimes cause headaches in certain individuals (especially those prone to migraines) is common knowledge—so much so that the phenomenon ("RWH") even has its own Wikipedia page. The Roman encyclopedist Celsus wrote in his treatise De Medicina about the pain felt after drinking wine, while six centuries later, Paul of Aegina mentioned that drinking wine could trigger a headache.

But the science to date is largely unclear regarding which components of red wine are responsible, as well as the mechanisms behind the phenomenon. A team of California scientists has narrowed down the likely culprits to a flavonol called quercetin, according to a new paper published in the journal Scientific Reports, although they have yet to run experiments with participants prone to RWH to test their hypothesis.

It's a knotty issue because of the complexities of both wine and human genetics/physiology. Wine is basically water and alcohol, along with acids, dissolved sugars, and other compounds that lend color and flavor. For instance, the tannins in wine are polyphenolic compounds responsible for much of the bitterness and astringency in a given wine; they're derived from the skins and stems of the grapes, or as a result of aging in oak barrels.

Red wines typically have more amines, sulfites, flavonoids, and tannins, particularly a phenolic compound with antioxidant properties called resveratrol, also found in grape skins and leaves. That's because red wines are typically produced by soaking the grape skins in the mash (maceration), while producing white wines involves immediately draining the juice away from the grape skins. The grape skins also contain anthocyanins, which give the wine its red hue.

Drink enough alcohol of any variety and you'll probably get a hangover that involves a headache and at least some nausea. What's unusual about RWH is that even small to moderate amounts of red wine can induce a headache. It's common these days to blame sulfites, a preservative that is a natural byproduct of fermentation, but white wine and many other foods also contain sulfites. In fact, white wine often contains more sulfites than red wine. There is a small percentage of the population that is allergic to sulfites, but they typically get hives and have trouble breathing rather than developing a headache.

Then there are biogenic amines, another fermentation byproduct that contains things like histamine and tyramine, both of which have been linked to headaches. Genetics is a factor here; some people just can't metabolize histamine very effectively, for instance, because they don't produce enough of the enzyme responsible for breaking it down in the small intestine. And alcohol inhibits that enzyme to begin with, resulting in higher histamine blood levels. This can dilate blood vessels, causing a headache. Those amines are also present in aged cheeses, cured charcuterie, and dried fruits—all of which are typically consumed with red wine, exaggerating the effects even more. However, at least one study found no correlation between histamine and RWH, although the sample size was very small.