Why do some wines give me a headache, but others do not?

Red wines are more apt to cause headaches. They contain more tannins than white wines. Tannins can increase serotonin in high enough levels to trigger headaches including migraine. Some red wines,like Merlot, have low tannin levels Some think it's the histamine in red grapes that is another cause of red wine induced headaches. Of course many people don't get headaches from drinking red wine.