You Should Never Put These 13 Things in the Dishwasher

Some social media food trends are overrated; others are unwise, or even unsafe. Earlier in the summer, TikTok creator @larad_official posted a series of cheeky videos that showed her mom cleaning produce like celery, carrots, and dragon fruit in… the dishwasher (on the rinse setting, with a little vinegar). 

To be clear, we don’t recommend doing this. Neither does the Food and Drug Administration (FDA), as dishwashers can harbor residual chemicals and unsafe pathogens. What’s more, it’s easy enough to wash your produce at home using good old water, pulling out a salad spinner if you’d like to work more quickly. 

Experts agree. “I always say, it’s called a dishwasher for a reason,” says Brandon Pleshek, a third-generation janitor and creator of Clean That Up. 

While cleaning produce in the dishwasher is one of the more off-the-wall ideas we’ve seen, there are quite a few cooking and tabletop pieces you should hand-wash when possible. If you put, say, an heirloom crystal dish in the appliance, you’re exposing something fragile to a humid environment, strong chemicals, and high water pressure. These things are great for cleaning up grime, but they can also wear down enamel, cast-iron seasoning, and blades over time. You also risk fractures, which is of course more important if you paid a lot of money for an item. 

Here are some common items you should always hand-wash. We’ve also included ones that are technically dishwasher-safe, but that you might want to reconsider before throwing into the dishwasher. 

Don’t do it

Kitchen knives

It doesn’t matter whether you’re washing a chef’s knife or a serrated knife. Unless it’s a butter knife, it doesn’t belong in the dishwasher, for a few reasons. Knives’ blades can dull in the dishwasher, and the handles can also become loose, making them less effective and safe over time. “It’s like throwing a fancy jacket into a washing machine. Just don’t do it,” says Ellen Marie Bennett, the founder of Hedley & Bennett and the host of kitchen makeover show Kitchen Glow Up.

Instead, hand-wash your knives with hot water and dish soap, but be sure to keep safety in mind so you don’t cut yourself in the process. Don’t place a kitchen knife in a sink full of hot soapy water for the next person to accidentally grab by the blade, and keep the blade facing away from you while cleaning it. “I usually push away from the blade with the sponge,” says Pleshek. 

Cast-iron 

It’s well-known but worth repeating: the dishwasher will destroy the seasoning on your cast-iron pan. To clean a cast-iron pan effectively, first scrape off any bits of food. You can add a few tablespoons of kosher salt and use a paper towel to scrub the pan. Pleshek also recommends using the cut side of a potato, which has oxalic acid that will fight rust, then using a little dish soap if you need. Dry immediately with paper towels to prevent rust, then re-season. 

Dutch oven

As with any cast-iron, cast-iron Dutch ovens should not go in the dishwasher. But even enameled cast-iron is off limits, since the dishwasher can break down the enamel over time. Instead, clean your Dutch oven with soap, warm water, and a non-abrasive sponge. If you have any caked-on messes, you can soak it with warm water and soap, or, for tougher messes, fill the pot with warm water and a couple tablespoons of baking soda, then bring it to a simmer for about eight to 10 minutes, per Le Creuset. Scrub and rinse. 

Anything wooden

Wood absorbs water, meaning your wooden cutting boards and spoons will swell and can eventually crack and break. They can also become musty and moldy. To minimize water exposure, wash wood pieces by hand with warm water and soap; Bennett and Kleshek both also recommend periodically rubbing wood pieces with a food-grade mineral oil, rubbing, then allowing it to dry on its side overnight.

To get rid of pesky stains, Pleshek swears by the old trick of using lemon and salt; apply coarse salt, scrub the surface with a lemon half, allow to sit for about five minutes, scrape off the residue, then rinse. 

Copper pots and pans

Dishwasher detergent and hot water can tarnish copper, so you’ll definitely want to clean any copper pots and pans manually. “Bar Keepers Friend makes it look brand new,” says Pleshek. He warns, however, that if you prefer a look with more patina, Bar Keeper’s Friend might make it look too new. In that case, use warm soap and water as usual. 

China, crystal, and other “fine” dishes

Just because you can put something in the dishwasher doesn’t mean you should. “If it’s a nicer item, just do it by hand,” says Bennett. “A little bit of extra elbow grease can go a long way for the longevity of a product that is just a little bit nicer than other stuff you have.” 

“A little dish soap and a non-scratch scrub sponge and you should be good,” adds Pleshek. 

Cheese graters, Microplanes, and other sharp objects 

As with other sharp blades, graters and other sharp objects should stay out of the dishwasher since the blades can dull. Pleshek adds that these sometimes have rubber or wooden handles that can warp or swell. They of course can be a little tricky to clean — Bennett suggests a scouring pad to “get into the nooks and crannies.” 

Insulated mugs

Most of these will already feature a disclaimer that they shouldn’t go in the dishwasher — and they shouldn’t! The dishwasher’s heat can damage the cup’s seals that allow hot drinks to stay hot and cold drinks to stay cold. Your best bet is to hand wash.

It depends

Plastic

The heat of the dishwasher can easily cause both soft and hard plastic items to warp, but since it tends to be less valuable, you can opt to throw it in if it’s labeled as dishwasher-safe. If you do, however, just don’t put plastic on the bottom rack, advises Plesherk. “That’s always where it gets really a lot warmer just because it’s closer to the heating element,” he explains. 

Sheet pans

Most sheet pans are technically dishwasher-safe, but you might opt to wash them by hand. If the sheet pan is corrugated, for example, excess water can collect in the pan and lead to rusting, says Pleshek. Bennett says she regularly puts her quarter sheet pans into the dishwasher without a problem. 

Nonstick pans

Teflon nonstick pans can be damaged by the dishwasher’s heat and chemicals. Some will advertise themselves as dishwasher-safe, but you should still be careful. “I personally don’t put mine in there because I don’t know how the heat is going to affect the coating,” says Pleshek. “If you paid a lot of money for a nice nonstick pan, you want it to be nonstick for as long as possible. So I err on the side of caution.” Ceramic nonstick pans are generally dishwasher-safe, but we still recommend washing by hand to prevent scratches.

Aluminum cookware

You generally shouldn’t put aluminum in the dishwasher, since it’s naturally reactive, and detergents can cause it to darken. Some aluminum pans are anodized and can go in the dishwasher, but you’ll want to be sure to check the manufacturer’s instructions. 

Blenders

Pleshek notes that many blender containers are dishwasher-safe on the top rack (you’ll still want to hand-wash the blade and the lid), but simply prefers to wash his manually for ease. “Let’s say I make a smoothie,” he says. “A great way to clean that quickly and efficiently is to pour out your smoothie, give it a quick rinse, and then fill it up halfway with water and a drop or two of dish soap and then just go run your blender as you normally would.” 

For what it’s worth, Bennett puts her trusty Vitamix container in the dishwasher. “Vitamixes are absolutely bulletproof and they have the greatest lifetime warranty of all time. So I’m a little less precious with it than I maybe should be,” she says with a laugh.