Many people say they are allergic to the Sulfites that they use to preserve the color of the wine. But, in researching this.. I found an article that argues that:
"Finally, recent evidence points to the presence of histamines in some wine (especially red wine) as being the real cuprit for some people with sensitivities. For the average person, drinking extra water after drinking wine is usually sufficient to help clear their system of any negative influence.
WOW! Thanks!