I know I've sure been confused to wake up with a headache after having a single glass of red wine. It doesn't seem to make any sense.
Scientists don't know either.
Sometimes sulfites are blamed. They are a compound that are naturally in wines. But sweet white wines frequently contain more sulfites than red wines, without the associated headaches. So sulfites are probably not what are causing the headaches.
The other possible culprit is biogenic amines. They are nitrogen-containing compounds that are found in plants and animals. Biogenic amines contain substances like histamine, which have been linked to allergic reactions. However, these would have to be present in much larger quantities than what is found in red wines for them to be the cause.
Besides, both sulfites and amines occur in many other foods that don't cause headaches.
So maybe something in the wine is enhancing the effects of sulfites or amines, or maybe something else entirely is the cause of red wine headaches.
But given the recorded benefits of red wine, I do wish I could enjoy a glass with a book in the evenings without playing Migraine Russian Roulette.
Do you get headaches from red wine? Have you noticed any trend with varietals and regions?
Some Useful Articles About Red Wine Headaches:
scienceline: Why does red wine give me a headache?
winegeeks: Red Wine Headaches