Alcohol gives wine its antiseptic properties.
It’s actually the polyphenols in grape skins, not ethanol (the type of alcohol in wine), that give wine the antibacterial and antioxidant properties to kill pathogens and prevent infection. (As an aside: isopropyl rubbing alcohol, 2x more toxic than ethanol, will disinfect most germs). During the Middle Ages, physicians of the time believed wine could cure most ills, but it was principally used to clean wounds. Because red wine has spent more time in contact with grape skins, accumulating more polyphenols, it was preferred over white. As the medieval water supply was often contaminated, doctors would also use wine to clean their surgical instruments. Hospitals often accepted vineyard plots as payments and made their own supply of medicinal vino. A number of hospitals (hôpital or hospice in French) in Europe built impressive cellars to store this pharmacopeia, and a few now operate as museums. The Cave Historique des Hospices de Strasbourg offers tours of the caves originally installed at the Hôpital Civil de Strasbourg in France in 1395. The Hôtel-Dieu museum in Lyon, France, commemorates the Hospices de Beaune, founded in 1443, which is funded by the celebrated annual wine auction of the same name each November.