Hi.
I was trying to remember the word sulphites, which are added to many or most commercial wines as a clarifier. Sulphites are said to be the cause of the headaches. Organic winemakers don't add them (although grape wines contain trace amounts naturally)
Anyway, in trying to recall the word, I did an internet search for wine additives, and the result is: I recommend not looking it up yourself, as it's rather disheartening.
And please enjoy your wine on my behalf too. I've been disqualified from drinking the stuff because of said headaches. Jeez, I loved the stuff too.
Aloha