Why Does Red Wine Cause Headaches?

Scientists have deciphered why red wine causes headaches. They suggest that phenolic flavonoids, compounds derived from grape seeds and skins, are to blame. These substances give red wine its color and flavor. In the body, these compounds are metabolized into substances that accumulate toxic acetaldehyde in the bloodstream. At high levels, it causes headaches, nausea, facial flushing, and sweating.