Even if you can’t list the ingredients in a Moscow Mule, you may be able to recognize one from across a bar: The simple combination of vodka, lime juice, and ginger beer is traditionally served in a copper mug. But that trendy vessel could pose a serious health threat, according to public health officials. As CBS News reports, the potential for food poisoning from those iconic cups is severe enough that the state of Iowa is taking a stand against them.

Copper is commonly used to make kitchenware like pots and pans, but when it comes into contact with certain foods, it can be unsafe. Foods and liquids that have a pH lower than 6.0, and are therefore acidic, can erode the copper and copper alloys and cause them to mix with whatever’s being consumed. The pH of lime juice falls between 2.0 and 2.35 [PDF], so the chances of copper contamination from a Moscow Mule sloshing inside a copper mug all night are high.

Symptoms of copper poisoning include vomiting, abdominal pain, diarrhea, and yellow skin or jaundice. Even if you feel fine after a night of Moscow Mule imbibing, long-term effects like liver damage can occur over time. In response to these hazards, Iowa’s Alcoholic Beverages Division released a statement [PDF] advising against the use of Moscow Mule mugs. “The recent popularity of Moscow Mules, an alcoholic cocktail typically served in a copper mug, has led to inquiries regarding the safe use of copper mugs and this beverage,” it reads. “The use of copper and copper alloys as a food contact surface is limited in Iowa.”

If you’re hesitant to put your Moscow Mule obsession to bed, there are ways to enjoy the drink safely without sacrificing the classic look. When stocking your bar at home, make sure to include copper mugs lined with food-safe metal like nickel or stainless steel. And when you’re ordering the drink elsewhere, you can check with the bartender to see if they have similar containers. If not, asking for the drink in a boring old glass is your safest bet.

[h/t CBS News]