Travel Mugs, Nonstick Pans and More Items That Don't Belong in the Dishwasher

CNET

10-07-2025

Whether you're learning the ropes of a brand-new dishwasher or you've been hands-free dishwashing for years, it's tempting to load it up and let it rip. It's summer -- you've got better things to do than babysit a sink full of dirty silverware.
But before you start stacking every spatula and chef's knife onto the racks, take a beat. Your dishwasher's high heat and aggressive cycles can do more harm than good to certain kitchen tools. Warping, rusting, cracking and dulling are all fair game -- even on items labeled "dishwasher-safe." And yes, that includes some of your priciest pieces.
If you want your gear to last, there are a few things you should always wash by hand, no matter how tempting that "Start" button is.
So before you run that next cycle, double-check what you're tossing in. Your spatulas, skillets and stemware will thank you.
11 things that should never go in the dishwasher.
1. Insulated mugs
Insulated mugs can be damaged by the pressure from a dishwasher.
The Darling Effect
The high heat and pressure of a dishwasher can damage or break the vacuum seal that makes these insulated vessels effective. Instead, wash them by hand using warm water and soap.
2. Wooden cutting boards
Always air-dry a wood board on its side for at least an hour before storing it.
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Wood cutting boards can become damaged after even one cycle through the dishwasher. Hot water can cause even the strongest wood to warp, bend, crack or split. While plastic and stone cutting boards can typically handle the dishwasher, any wooden slab should be washed by hand and dries thoroughly on its side.
Read our guide to wooden cutting board care for more.
3. Wine glasses
Wine glasses and other thin pieces of barware should be hand washed to avoid breaking.
CB2
90% of wine glasses are unfit for the dishwasher. If you have thick, sturdy glasses, they may fare OK, but thin and delicate wine glasses are likely to break. Instead, wash them by hand and be sure to rinse them well so there's no soapy residue messing with your next wine's balanced bouquet.
4. Kitchen knives
Always wash good cutlery by hand.
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If you've got a sharp chef's knife and want to keep it that way, keep it out of the dishwasher. Not only will the extended soaking in hot water compromise the blade's edge, but the dishwasher could send your knife clanking about and knocking in to other items that will ding and dull the blade.
Here's a list of other bad habits that are ruining your knives.
5. Antiques, porcelain and fine China
Delicate China and porcelain is susceptible to breakage.Antique cookware, bakeware and glassware isn't a good candidate for the dishwasher. Even if it's labeled "dishwasher-safe," it's age may have compromised a once rugged integrity, making it prone to chipping or cracking. If you have vintage cookware, kitchen tools or China you love, protect them by hand washing in the sink.
While porcelain itself is dishwasher safe, porcelain wares are often thin and brittle, and running them through the dishwasher puts them at risk.
6. Nonstick cookware
Nonstick cookware can lose its chemical coating in the dishwasher.
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Most nonstick cookware is technically safe to load into the dishwasher, but that doesn't mean it's a good idea. Nonstick surfaces are easily scratched and eroded when pummeled with hot water and soap or rubbed and knocked against other pots, pans or plates.
7. Copper cookware
Stainless steel is mostly dishwasher safe by copper cookware should be hand washed.
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While I don't advocate for putting any good cookware in the dishwasher, copper cookware is especially susceptible to damage. Copper will dull and tarnish from long exposure to hot water and the metal is soft, making it vulnerable to dings and dents if knocked against other items in the rack.
8. Cast-iron cookware
Use salt and hot water to get stubborn bits off of cast-iron cookware.
Lodge
You've worked so hard to build up a layered seasoning and slick patina on your cast-iron skillet, and one cycle through the dishwasher has the potential to strip it all away. Harsh dish detergent is likely to reek havoc on the surface while extended soaking in hot water can cause rust. Instead, use this pantry staple to clean stubborn cast-iron pans.
9. Oil and grease
You can clog the dishwasher with just one greasy pan.
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Your instinct when confronted with a greasy, oily pan may be to huck it in the dishwasher and hope for the best. Oil and grease are notorious for causing clogs in dishwashers -- and sinks for that matter.
Instead, try to discard as much of the oil as possible into the trash with a scraper or paper towel and hand wash your oily cookware well with soap and hot water. Only then, when most of the grease is removed, should you consider running it through the dishwasher.
10. Wooden utensils
Wooden utensils and hot water are not a good mix.
Getty/Kenny Williamson
Anything made from wood can be ruined if run through the dishwasher. That includes cooking utensils, spoons, chopsticks, bowls and anything else. Wooden items should always be hand washed and dried quickly and thoroughly to avoid splitting, warping and bacteria growth.
11. Plastic cups and containers
Food storage containers go in looking like this but come out looking like something from a Dali painting.
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Acrylic bowls and other strudy plastics are fine to run through the dishwasher, but flimsier plastic containers are not. Most takeout boxes and food storage containers will melt when hit with boiling hot water. Plastic cups are also susceptible to melting and should be hand washed instead.