Here are 8 things you should absolutely NOT put in a dishwasher, along with why each one gets damaged or causes problems:
1. Wooden items (spoons, cutting boards, bowls)
Why not:
- High heat and water soak the wood
- Causes cracking, warping, and splitting
- Removes natural oils, making wood rough and dull
Result: Wood becomes unusable or unhygienic over time.
2. Cast iron cookware
Why not:
- Dishwasher strips the seasoning layer (protective oil coating)
- Leads to rusting almost immediately
- Harsh detergents damage the surface
Result: Food starts sticking, and pan corrodes.
3. Non-stick pans (Teflon-coated)
Why not:
- Dishwasher heat and detergents degrade the coating
- Causes peeling or loss of non-stick performance
- Shortens lifespan significantly
Result: Food sticks, and coating may become unsafe.
4. Sharp knives (chef knives, paring knives)
Why not:
- Blades knock against other items → become dull quickly
- Water + detergent can cause corrosion
- Handles (especially wood) may loosen
Result: Knife loses sharpness and becomes unsafe.
5. Aluminum cookware and utensils
Why not:
- Detergents react with aluminum → dark stains or discoloration
- Can cause pitting and surface damage
- Loses shine permanently
Result: Looks old and worn even if still usable.
6. Crystal glassware or fine china
Why not:
- High heat causes clouding or cracking
- Fragile items can chip due to vibration
- Detergent may etch delicate surfaces
Result: Expensive items lose clarity and value.
7. Insulated travel mugs and thermoses
Why not:
- Dishwasher heat can break the vacuum seal insulation
- Water may get trapped inside layers
- Reduces ability to keep drinks hot or cold
Result: Mug stops insulating properly.
8. Copper cookware and utensils
Why not:
- Dishwasher chemicals cause tarnishing and dullness
- Removes protective coating or polish
- Can create permanent stains
Result: Copper loses its bright, shiny appearance.
Quick Rule of Thumb:
If something is handmade, coated, insulated, wooden, or delicate, it usually does NOT belong in a dishwasher.
If you want, I can also give you:
- A list of things that ARE dishwasher-safe
- Or “hidden items people mistakenly ruin in dishwashers” (very useful list)