If a person experiences diarrhea more when they drink wine, they may have an allergy to tannins. Tannins are compounds found in the skin of grapes, and a reaction to them may cause symptoms of headaches, nausea, and diarrhea. Excessive sugar from mixed drinks can also make diarrhea worse for some people.
Fermented drinks and non-distilled alcoholic beverages (think beer, lager, cider, and wine) increase acid secretion in the stomach by stimulating gastrin secretion. High alcohol doses slow gastric emptying and bowel motility — which can be constipating.
Alcohol use interferes with the normal digestive process, leading to diarrhea after drinking. Alcohol use often causes the stomach to produce more gastric acid, increasing inflammation and irritation. Most often, beer and wine produce this effect, and this can produce diarrhea.
“Red wine is kind of the trifecta,” Bonci says. Not only does it have histamines and sulfites, but it also has a protein found in grape skin called LTP. This protein gives red wine its color, but it might induce allergic responses in certain people which include flushing, and even diarrhea.