Many items labeled “dishwasher-safe” are fine, but some common household objects can be damaged—or damage your dishwasher—if washed this way.
1. Sharp Kitchen Knives
Why not?
- High heat and detergent can dull the blade.
- Knives can bang against other items.
- They can be dangerous when unloading.
2. Cast Iron Cookware
Why not?
- Dishwasher detergent strips away the seasoning.
- Prolonged moisture can cause rust.
3. Wooden Utensils and Cutting Boards
Why not?
- Heat and water can cause warping, cracking, and splitting.
- Wood may lose its finish over time.
4. Nonstick Pans (Some Types)
Why not?
- Repeated dishwasher cycles can shorten the life of the nonstick coating.
- Check the manufacturer’s instructions.
5. Fine Crystal and Delicate Glassware
Why not?
- Heat and strong detergents can cause clouding, etching, or cracking.
- Delicate stems may break.
6. Copper, Brass, and Certain Aluminum Items
Why not?
- Dishwasher detergents can discolor or tarnish these metals.
- Aluminum may become dull or develop dark spots.
7. Insulated Travel Mugs and Bottles
Why not?
- Some have vacuum seals that can be damaged by dishwasher heat.
- Always check whether the manufacturer specifies dishwasher safety.
8. Antique, Hand-Painted, or Valuable Items
Why not?
- Decorations, paint, and finishes may fade or peel.
- Older adhesives and materials can deteriorate.
Bonus: Things That Can Damage the Dishwasher
Avoid putting in:
- Large food scraps
- Wax-coated items
- Labels that can peel off
- Fragile plastics not marked dishwasher-safe
A Simple Rule
If an item is made of wood, cast iron, delicate glass, specialty metal, or has a sharp edge, hand-washing is often the safer choice unless the manufacturer specifically states it is dishwasher-safe.
