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How to Clean Mold from Under Your Travel Mug's Lid, According to a Cleaning Expert

May 31, 2023May 31, 2023

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When was the last time you hand washed your YETI mug? Exactly.

We all know that reusable cups and straws are the way to go. The tough part, however, is making sure that what we're drinking out of is actually clean. Even though most popular tumblers are dishwasher-safe, it doesn't mean that your dishwasher safely and effectively cleans them.

In fact, many travel mugs have removable seals to trap in heat or cold — and if they aren't properly cleaned and dried, these seals also trap moisture. Mold, which is a type of fungus, flourishes in moist, dark areas. Yep, that means with every sip of coffee, you're probably also drinking mold if your lid hasn't been properly cleaned.

After hearing that this was causing people to get sick, Veronica Lucas took a closer look at her travel mug and discovered tons of mold hidden underneath the lid's removable seal. She shared photos to Facebook, and the post went viral with 16,000 likes and more than 2,000 comments.

Veronica's not alone. In October 2018, Dr. Beau Pierce, a sports chiropractor based in Santa Maria, California, posted a now-viral video titled "A Yeti Style Cup Almost Killed My Patient." In the video, he explains how one of his patients mentioned how he was struggling to beat an ongoing sickness. After asking a series of questions, Dr. Beau noticed his patient's tumbler sitting on the counter and upon taking a closer look, discovered mold hidden underneath the lid.

It's a bit extreme to say that a tumbler was killing his patient, but the connection between a moldy lid and sickness is very likely. Consuming mold, at any degree, isn't good for your health. "Some molds cause allergic reactions and respiratory problems. And a few molds, in the right conditions, produce 'mycotoxins,' poisonous substances that can make you sick," according to the USDA.

While the YETI name is being thrown around, this is a common problem with all tumblers that have removable seals, no matter the brand. YETI, however, responded to with the following statement:

On their FAQ page, YETI explains that just sticking it in the dishwasher won't necessarily do the dirty work: "And here's an extra tip to prolong the life of your YETI cup: before it goes in the dishwasher, remove the rubber lid gasket to prevent any grime build up in the lid. Then throw it in the silverware basket." So, there. The solution has been in front of our faces all along.

To prevent mold, Carolyn Forte, Director of the Home Appliances and Cleaning Products Labs at the Good Housekeeping Institute, recommends that you scrub any areas that the dishwasher can't reach. "To get rid of all the residue and resulting mold, you should totally disassemble the tumbler and scrub all the pieces by hand in hot, soapy water to be sure they are clean," she explains. "These cups and thermal carafes have removable seals for a reason."

Her top tip: Stick it in the dishwasher before you wash it by hand. "While the dishwasher is great, it can’t do everything, and it can’t clean under these seals. In fact, water from the dishwasher can actually get trapped in there, which causes mold to grow." No, thanks!

To be clear: We're not telling you to ditch your tumblers altogether. This is simply a friendly reminder to give your reusable to-go cups a regular deep clean.

Amanda Garrity is a lifestyle writer and editor with over seven years of experience, including five years on staff at Good Housekeeping, where she covered all things home and holiday, including the latest interior design trends, inspiring DIY ideas and gift guides for any (and every) occasion. She also has a soft spot for feel-good TV, so you can catch her writing about popular shows like Virgin River, Sweet Magnolias, Hallmark Channel’s When Calls the Heart and more.

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Yep, that means with every sip of coffee, you're probably also drinking mold if your lid hasn't been properly cleaned.