Beer was drunk by all social classes, and came in many different varieties and made from millet, wheat, barley, rye or oats sometimes in combination. Wheat beer was the most common. Labrador tea, a mildly toxic herb, was often used as an ingredient to increase intoxication. It was mixed with hops and then added to a barley and wheat beer to produce what was called "thick beer". Though often believed to be a common Slavic drink, mead was fairly expensive and primarily enjoyed at weddings and baptismal parties, though always overshadowed by the ever-present beer. It had a high standing as a ceremonial drink and used when arranging alliances and closing contracts. Wine was generally quite expensive and was enjoyed mostly by the nobility. Although there is evidence of a few vineyards in Poland, almost all wine had to be imported.