Think everything can go in the dishwasher? Think again. Discover 8 common kitchen items that can be damaged by dishwasher heat, detergent, or powerful water jets.
8 Things You Absolutely Shouldn’t Wash in the Dishwasher
A dishwasher can save a huge amount of time, especially after a large family meal. Instead of standing at the sink washing every plate, glass, and utensil by hand, you can load the machine, add detergent, and let it do the work.
But there is one important catch: not everything in your kitchen belongs in the dishwasher.
High temperatures, strong detergents, powerful water jets, and long drying cycles can damage certain materials. Some items may become dull, warped, cracked, rusty, or completely unusable after repeated dishwasher cycles.
Before you toss another kitchen item into the rack, here are eight things that are usually better washed by hand.
1. Wooden Cutting Boards and Utensils
Wooden spoons, wooden cutting boards, rolling pins, and other wooden kitchen tools generally shouldn’t spend much time in a dishwasher.
The combination of hot water, steam, detergent, and prolonged drying can cause wood to swell and contract repeatedly. Over time, this may lead to:
- Cracks
- Warping
- Splitting
- Rough surfaces
- Loose joints or handles
Once a wooden utensil develops cracks, food particles and moisture can become trapped inside them.
Better option: Wash wooden items by hand with warm water and mild dish soap. Avoid soaking them for long periods, then dry them thoroughly.
2. Cast-Iron Cookware
Cast-iron skillets and pans are famous for their durability, but the dishwasher is not their friend.
Dishwasher detergent and prolonged exposure to water can strip away the seasoning that gives cast iron its naturally nonstick cooking surface. Continued exposure to moisture can also encourage rust.
That doesn’t mean cast iron is difficult to maintain.
After cooking, clean it according to the manufacturer’s recommendations, dry it thoroughly, and maintain the seasoning when necessary.
A properly maintained cast-iron pan can last for generations.
3. Good Kitchen Knives
Your everyday inexpensive table knives may be dishwasher-safe, but high-quality chef’s knives are usually better washed by hand.
Dishwasher conditions can be rough on sharp blades. Knives can knock against other utensils, potentially damaging the edge. Dishwasher detergent and high heat may also affect handles or finishes on certain knives.
There is also a safety issue: reaching into a dishwasher containing exposed sharp blades increases the possibility of an accidental cut.
Better option: Wash expensive or high-quality knives individually by hand and dry them immediately.
4. Nonstick Pans
Many modern nonstick pans come with specific dishwasher instructions, so always check the manufacturer’s label first.
However, repeated dishwasher cycles can shorten the useful life of some nonstick cookware. Strong detergents, high temperatures, and abrasive conditions may gradually wear down the coating.
Even if a pan is technically labeled dishwasher-safe, hand-washing it gently can sometimes help preserve its finish for longer.
Use a soft sponge rather than an abrasive scrubber and avoid aggressive scraping.
5. Crystal and Delicate Glassware
Beautiful crystal glasses and delicate stemware deserve extra care.
Dishwashers expose glassware to high temperatures, strong detergent, water pressure, and the possibility of bumping into neighboring dishes.
Over time, delicate glass can become cloudy, scratched, or damaged. Thin stems can also be particularly vulnerable to breakage.
If the glassware is valuable, antique, unusually thin, or has special decoration, hand-washing is generally the safer choice.
Use lukewarm water, a small amount of mild detergent, and a soft cloth or sponge.
6. Copper Cookware
Copper pots and pans can develop their distinctive shine and appearance over time, but putting them in the dishwasher can cause unwanted discoloration or damage to the finish.
Some copper cookware has protective coatings or decorative finishes that may not tolerate dishwasher detergents well.
If you want to preserve the appearance of copper cookware, check the manufacturer’s instructions and wash it by hand when recommended.
For decorative copper pieces, hand-cleaning is usually the safer approach.
7. Items With Delicate Decorations or Printed Designs
Not everything that looks like ordinary ceramic or glass is dishwasher-safe.
Mugs, plates, serving pieces, and glasses with:
- Gold or silver trim
- Hand-painted designs
- Decorative decals
- Metallic details
- Vintage finishes
may gradually lose their appearance in the dishwasher.
Repeated exposure to heat and detergent can cause decorative details to fade, peel, or become dull.
If the item has sentimental or monetary value, don’t assume that because it looks sturdy it can survive hundreds of dishwasher cycles.
8. Certain Insulated Travel Mugs and Containers
Travel mugs, insulated bottles, and vacuum-insulated containers require special attention.
Some are specifically designed to be dishwasher-safe, while others aren’t. Heat and dishwasher conditions may damage certain seals, finishes, lids, or insulation components.
A particularly important area is the lid. Many travel containers have multiple small pieces, silicone seals, valves, or removable components that need to be cleaned separately.
Always check the manufacturer’s instructions before putting an insulated container in the dishwasher.
What About Plastic Containers?
Plastic is not automatically dishwasher-safe or dishwasher-unsafe.
Look for the manufacturer’s dishwasher-safe symbol or instructions. If the container is labeled dishwasher-safe, place it where recommended — often on the upper rack.
Avoid putting questionable plastic containers directly above or near the heating element, where temperatures can be particularly high.
Older, thin, or disposable plastic containers are more likely to warp or become damaged.
Why Does the Dishwasher Cause So Much Damage?
A dishwasher isn’t simply a sink that happens to wash dishes automatically.
Inside the machine, items may encounter:
High heat: Hot water and drying cycles can affect sensitive materials.
Strong detergent: Dishwasher detergent is formulated for tough food residue and can be harsher than ordinary hand dish soap.
Powerful water jets: Lightweight or delicate objects can move around during a cycle.
Long exposure to moisture: Materials such as untreated wood can absorb water and change shape.
Mechanical contact: Items that bump into one another repeatedly can develop chips, scratches, or cracks.
The combination of these factors explains why an item that survives one dishwasher cycle may still deteriorate after months or years of repeated washing.
A Simple Rule Before Loading the Dishwasher
Before putting an unfamiliar item inside, ask yourself three questions:
Is it made of wood, cast iron, or another delicate material?
Does it have a special finish, decoration, coating, or insulation?
Does the manufacturer specifically say it is dishwasher-safe?
If you’re unsure, hand-washing is usually the safer choice.
Don’t Forget to Read the Manufacturer’s Instructions
The biggest exception to every dishwasher rule is the product’s own care instructions.
Manufacturers may use different materials, coatings, adhesives, finishes, and construction methods. Two pans that look almost identical may have completely different dishwasher recommendations.
So if an item is expensive, sentimental, unusually delicate, or made from multiple materials, check the label, packaging, or manufacturer’s care instructions before washing it.
Final Thoughts
A dishwasher is incredibly convenient, but convenience doesn’t mean every kitchen item should go inside it.
Wooden utensils, cast iron, quality knives, delicate glassware, copper cookware, decorative dishes, certain nonstick cookware, and some insulated containers can require extra care.
When in doubt, wash the item by hand. A few extra minutes at the sink can be much cheaper than replacing a favorite pan, knife, glass, or family heirloom.