Why You Should Think Twice About Taking That Cup of Joe into the John with You

Updated: Mar. 04, 2017

If you ever hit up the bathroom with your coffee cup in tow, you may be leaving with a cup full of (microscopic) bathroom bugs. Ew!


Maybe you’re on your way to get a refill or your heading to the kitchen area to wash it out—and nature calls when you’re on your way, so you figure why not make a pit stop. We get it. But you may want to think twice before you do.

Turns out your coffee and mug could pick up “bathroom bugs” aka fecal bacteria, explains Donna M. Duberg, MA, assistant professor, Department of Biomedical Laboratory Science at Saint Louis University in St. Louis, Missouri. “Depending on how many bacteria we ingest and how healthy we are, we could get mildly to very ill with nausea, vomiting, or diarrhea.” Duberg says that it might even lead to catching salmonella, shigella, and listeria, which are all spread through fecal bacteria.

Think putting on a lid on it will make a difference? Think again. It’s not the liquid inside that cup that’s the problem. (In fact, the hot coffee should keep the growth of bacteria and viruses at bay.) It’s the outside of that lid and mug that could be infested with bacteria. And whatever you do, don’t bring that cup into the stall with you. Duberg warns, “When you flush the toilet there are over 3 million bacteria per square inch of that toilet bowl and the aerosol that flies up can land all over your mug.”

But what if the lavatory sink is the only one available to clean your favorite “Keep Calm And Drink Coffee” mug? Duberg recommends following this “washing ceremony” to avoid contamination as much as possible: “Put down some clean paper towels on the side of the sink just before the mug is washed, clean it thoroughly, rinse it well with clear running water, drain the mug on the clean paper towels, get more clean paper towels to dry it off, and leave without letting it touch the counter. Use clean paper towel(s) to open the door and return to your desk.”

The good news is if the only reason you’re bringing that mug in to the John with you is to wash it (and we really hope it is!) it might be more sanitary to not wash it at all. Turns out, it’s OK to never wash your mug, as long as you’re not sharing it with anyone else or taking your coffee light and sweet—leaving cream and sugar behind can cause mold to grow.

Ultimately, the best way to get that mug clean is to run it through the dishwasher, which can achieve temperatures high enough to kill bacteria. But if you have to hand wash your mug, avoid doing it in the bathroom.