The Worst Things to Put in the Dishwasher, According to Cleaning Experts

When it comes to handy household appliances, the dishwasher is hard to beat. It takes over one of the most dreaded chores — washing the dishes. But even though a dishwasher makes daily cleaning more manageable, it does have limitations.

We recently interviewed cleaning experts to get the lowdown on what you should keep out of your dishwasher. Here’s what they had to say.

Worst Things to Put in the Dishwasher

Certain Types of Plastic Dishes, Cups, and Utensils

Plastic dishes are more economical than glass, which is a big reason you can find them in most households. However, not all plastic is dishwasher safe, says Ryan Knoll of the home cleaning service, Tidy Casa. “We’re wary of plastics that could warp or release chemicals under high heat,” says Knoll. “If it’s not clearly marked as dishwasher safe, we’re washing it by hand to err on the side of caution.”

Before you throw your new plastic piece in the dishwasher, check on the bottom for a dishwasher-safe symbol. Even some plastic that is dishwasher safe doesn’t hold up well under high heat. Thin plastic lids that come on Tupperware containers, for example, can crack when repeatedly cleaned in the dishwasher.

Pre 1970’s China Dishes

Dishwashers became commonplace in the 1970s. Before then, everyone had to wash every dish and utensil by hand. Because of that, pre-1970s China is not dishwasher safe, says Aaron Christensen of Homeaglow. “These fragile dishes were not made for dishwashers because they weren’t common household items. Certain brands and styles could leach metals or have the etched designs worn away. Safeguard your family heirlooms and hand wash them!”

Wooden Cutting Boards and Utensils

All of our cleaning experts agreed — putting wooden cutting boards and utensils in the dishwasher is a big no-no. When steam and hot water come into contact with the wood, it can expand and contract. Repeated exposure will lead to warped or cracked wood.

It’s best to handwash all wooden utensils with gentle soap and water. You can even clean your wooden cutting board with lemon juice and salt instead of placing it in the dishwasher.

Non-Stick Pans

Most non-stick pans are dishwasher safe, but that doesn’t mean the dishwasher is the best way to clean them, says Will Cotter of Fresh Space Cleaning. “They typically feature a coating that can be sensitive to high temperatures, abrasive detergents, and intense mechanical action—factors commonly found in dishwashers. While many manufacturers claim their pans are dishwasher-safe, the repeated exposure to the dishwasher’s heat and chemicals can gradually degrade the non-sticknon-stick surface. This might lead to diminished non-sticknon-stick properties over time.”

He recommends handwashing non-stick pots and pans with water, mild soap, and a soft sponge.

Knives (And Anything Else that’s Sharp)

Want to keep your knives, cheese grater, and kitchen scissors sharp? Keep them out of the dishwasher. Repeated exposure to high heat, water pressure, and some dish detergents can dull knives quickly. It’s best to handwash all sharp kitchen tools with a soft sponge, dish soap, and water.

Insulated Travel Mugs

Most coffee travel mugs are advertised as dishwasher safe, and while running them through the dishwasher won’t release toxic chemicals, it can damage them. Ryan Knoll advises, “a trip through the dishwasher can compromise the insulation, leaving you with a lukewarm coffee situation.”

The dishwasher’s high heat can also damage cups or lids with rubber gaskets. It’s best to hand wash your stainless steel and insulated water bottles and coffee mugs.