How Often You Should Wash Your Office Coffee Mug May Surprise You

Empty coffee mugs in kitchen sink being washed

Photo: StudioLightAndShade /Depositphotos

Many office workers have a beloved coffee mug that they cling to for dear life. It's common for people to become possessive over their precious cup, which serves both as a vessel for their caffeine boost and an expression of their personality. It also acts as a conduit for warm drinks which have been shown to improve metaphorical feelings of warmth. Despite the comfort the humble office mug may bring, researchers have suggested that there might be something sinister lurking within.

Dr. Charles Gerba, microbiologist and professor at the University of Arizona, told LifeHacker that “around 90% of most office coffee mugs harbor dangerous germs, and 20% of those carry fecal bacteria.” Where are those dangerous germs coming from? Probably the cleaning process itself. Kitchen sponges and sinks are rife with bacteria and viruses that make your toilet pale in comparison. A communal sink and sponge only exacerbates the problem as they are cesspools for germs.

Is this vindication for the less hygienically minded among us who are happy with a quick rinse of their mugs? Maybe. But don't let sugar or milk sit in your mug. As infectious-disease expert Jeffrey Starke, professor at Baylor College of Medicine, explains, “If you leave cream or sugar in your mug over the weekend, that can certainly cause mold to grow.” In that case, the best solution is taking your mug home to wash it. Alternatively, you can avoid touching kitchen surfaces and only use disposable paper towels during your wash-up. Of course that might be frustrating news to the eco-conscious who only have a reusable mug to limit paper waste.

So, what's the answer to the age-old question How often should you wash your office coffee mug? Ultimately, there is no clear-cut solution for all. For extra precaution, the main pieces of advice appear to be to rinse your office cup after every use, avoid using a communal sponge, and take the cup home for a clean in the dishwasher each day.

Scientists encourage washing your office coffee mug often, but not necessarily with a sponge.

Coffee mugs that need to be washed, or rinsed

Photo: Zetor2010/Depositphotos

If you keep your coffee mug in an office kitchenette, it's bound to have bacteria on it and the likelihood of dangerous germs is greater with the use of a communal sponge.

Stained coffee mugs seen from above

Photo: seb_ra/Depositphotos

Microbiologists suggest that “around 90% of most office coffee mugs harbor dangerous germs, and 20% of those carry fecal bacteria.”

Scientist with blue latex gloves on holding and looking at a coffee mug

Photo: AI-generated image via Depositphotos

So, your best option is to rinse your cup in the office, and then take it home for a cleaning in the dishwasher.

Woman loading a dishwasher with coffee mugs

Photo: NewAfrica/Depositphotos

h/t: [IFL Science]

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Elizabeth Beiser

Elizabeth Beiser is a Contributing Writer and Project Coordinator at My Modern Met. She has a background in American Cultural History with a special focus on Modern art and democratic community building. She received her B.A. in history, with a minor in Studio Arts, and her M.A. in history from the University of Rochester. She has worked on multiple political campaigns, as well as in non-profit operations and direct service. When she’s not writing, she’s experimenting with all varieties of arts and crafts. She also enjoys spending time with four-legged friends and exploring her hometown of Boston.
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