1. Cast iron cookware
Why avoid it:
- Dishwasher detergent can remove the seasoning (the protective oil layer).
- Excess moisture can cause rust.
- The surface may become rough and less nonstick.
Better: Wash with warm water, a brush or sponge, and dry immediately. Add a thin layer of oil if needed.
2. Wooden utensils, cutting boards, and bowls
Why avoid it:
- Heat and prolonged soaking can make wood swell, crack, warp, or split.
- Dishwashing can strip natural oils from the wood.
Better: Hand wash and dry upright.
3. Sharp knives
Why avoid it:
- Dishwasher detergent and heat can dull blades.
- Knives can bump against other items or damage the dishwasher racks.
- Loose knives can be a safety hazard when unloading.
Better: Wash by hand and dry immediately.
4. Nonstick cookware
Why avoid it:
- Repeated dishwasher cycles may degrade the nonstick coating.
- Harsh detergents can shorten the pan’s lifespan.
Better: Hand wash with a soft sponge unless the manufacturer specifically says it is dishwasher safe.
5. Crystal glassware and delicate glass
Why avoid it:
- High temperatures and strong sprays can cause chips, cracks, or cloudiness.
- Some crystal contains minerals that can be damaged by dishwasher detergents.
Better: Hand wash delicate glasses.
6. Copper, brass, and some aluminum items
Why avoid it:
- Dishwasher detergents can cause discoloration, tarnishing, or a dull finish.
- Aluminum may develop dark or cloudy spots.
Better: Clean according to the metal type’s care instructions.
7. Insulated travel mugs and some reusable bottles
Why avoid it:
- Heat can damage seals or vacuum insulation in some products.
- Water may get trapped between layers.
- Printed designs or coatings may peel.
Better: Check the manufacturer’s label; many are only top-rack dishwasher safe.
8. Items with glued parts or delicate decorations
Examples:
- Antique dishes
- Hand-painted ceramics
- Some knives with glued handles
- Decorative serving pieces
Why avoid it:
- Heat and detergent can weaken adhesives.
- Designs and finishes may fade or peel.
Better: Hand wash to preserve them.
Dishwasher-safe items that often surprise people
Many modern items are safe if labeled dishwasher-safe, including:
- Stainless steel utensils
- Most everyday ceramic plates
- Glass baking dishes
- Some plastic containers (usually top rack only)
Tip: When in doubt, check the manufacturer’s care instructions—dishwasher safety depends on the material, coating, and construction.
