Here are 8 things you should never put in the dishwasher, with detailed explanations of why they can be damaged and what to do instead.
1. Wooden utensils, cutting boards, and bowls
Why you should avoid the dishwasher:
- The high heat and long exposure to water cause wood to absorb moisture and swell.
- Repeated dishwasher cycles can make wood crack, warp, split, or lose its smooth finish.
- The detergent can remove natural oils from wood, making it dry and brittle.
- Wooden items may develop gaps where bacteria can collect.
Examples:
- Wooden spoons
- Bamboo cutting boards
- Wooden salad bowls
- Wooden spatulas
Better method:
Wash wooden items by hand with warm water and mild soap. Dry them immediately and occasionally treat them with food-safe mineral oil.
2. Cast iron cookware
Why you should avoid the dishwasher:
- Dishwasher detergent removes the protective seasoning layer that gives cast iron its non-stick surface.
- Water exposure can cause rust formation.
- The pan may lose its cooking performance and develop uneven seasoning.
Examples:
- Cast iron skillets
- Dutch ovens
- Cast iron griddles
Better method:
Clean cast iron with warm water, a soft brush or sponge, and minimal soap if needed. Dry completely and apply a thin layer of oil.
3. Sharp knives
Why you should avoid the dishwasher:
- Dishwasher cycles can dull knife blades because they may hit racks or other utensils.
- Strong detergents can damage the metal surface.
- Moisture can cause corrosion, especially on high-carbon steel knives.
- Loose knives can also damage dishwasher racks or become a safety hazard when unloading.
Examples:
- Chef’s knives
- Paring knives
- Japanese knives
- Carving knives
Better method:
Wash knives by hand immediately after use and dry them thoroughly.
4. Non-stick cookware
Why you should avoid the dishwasher:
- High temperatures and harsh detergents can weaken the non-stick coating.
- Over time, the coating may peel, scratch, or lose its effectiveness.
- Damaged coatings can cause food to stick and shorten the life of the pan.
Examples:
- Non-stick frying pans
- Non-stick baking trays
- Teflon-coated cookware
Better method:
Wash gently with a soft sponge and avoid abrasive cleaners.
5. Copper cookware and copper items
Why you should avoid the dishwasher:
- Dishwasher detergent can cause copper to lose its shine.
- Chemical reactions may create discoloration or dark spots.
- Decorative copper items may become permanently damaged.
Examples:
- Copper pots
- Copper mugs
- Copper measuring cups
- Decorative copper pieces
Better method:
Hand wash with mild soap. Use a copper cleaner or a gentle natural cleaner if polishing is needed.
6. Crystal glasses and delicate glassware
Why you should avoid the dishwasher:
- High heat and strong water pressure can cause cracks or chips.
- Dishwasher detergent can make crystal appear cloudy.
- Delicate glass can break when it touches other items during the cycle.
- Some crystal contains minerals that react poorly with dishwasher chemicals.
Examples:
- Crystal wine glasses
- Antique glassware
- Hand-painted glass cups
Better method:
Wash delicate glassware by hand using warm water and mild detergent. Dry with a soft towel.
7. Graters, garlic presses, and fine kitchen tools
Why you should avoid the dishwasher:
- Small holes and sharp edges can trap food particles.
- Dishwasher cleaning may not fully remove stuck ingredients.
- Some tools have joints or moving parts where water and detergent can cause corrosion.
- Sharp edges may damage dishwasher racks.
Examples:
- Cheese graters
- Garlic presses
- Zesters
- Fine mesh strainers
Better method:
Clean immediately after use with a brush and warm water.
8. Insulated bottles, travel mugs, and some thermoses
Why you should avoid the dishwasher:
- Many insulated products rely on a vacuum layer between walls. Excess heat or water pressure may damage seals.
- Dishwasher detergent can damage exterior coatings.
- Water can enter areas around lids, causing odors or mold.
- Some travel mugs lose their insulation ability over time.
Examples:
- Stainless steel travel mugs
- Vacuum bottles
- Insulated water bottles
Better method:
Wash by hand with warm soapy water. Clean lids and seals separately.
Other items you should be careful with
- Aluminum cookware: may become dull or discolored.
- Non-dishwasher-safe plastics: can melt or release odors.
- Hand-painted dishes: designs may fade.
- Antique dishes: may crack or lose their finish.
- Pressure cooker parts: some seals and valves can be damaged.
Quick rule to remember:
If an item is wooden, sharp, delicate, coated, handmade, antique, or made from reactive metals, it is usually safer to wash it by hand.
Always check the manufacturer’s label—some modern items are specially designed to be dishwasher safe.