Here are 8 things you should never put in the dishwasher, and why it can damage them or the machine:
1) Wooden utensils or cutting boards
Dishwasher heat and water cause wood to:
- Crack
- Warp
- Lose protective oils
Over time, they become rough and unhygienic.
2) Nonstick pans
High heat and harsh detergent can:
- Strip the nonstick coating
- Make food stick permanently afterward
Handwashing keeps them usable much longer.
3) Cast iron cookware
Dishwashers remove the seasoning layer and cause:
- Rust
- Loss of nonstick surface
Cast iron needs oil and dry hand cleaning only.
4) Sharp knives (chef knives, etc.)
Dishwashers can:
- Dull blades quickly
- Cause handles to loosen over time
They also pose a safety risk when unloading.
5) Crystal glassware
Heat and pressure can:
- Cloud the glass
- Cause cracks or chips
Handwashing preserves clarity and shine.
6) Insulated travel mugs / thermoses
Dishwasher water can get between layers and:
- Ruin insulation
- Cause trapped odors or mold
Many are labeled “hand wash only” for this reason.
7) Aluminum cookware
Dishwasher detergents can react with aluminum, leading to:
- Darkening or staining
- Pitting on the surface
8) Anything with delicate decals or glue (some plastics, bottles, containers)
Hot water and detergent can:
- Fade prints
- Weaken adhesives
- Warp thin plastic
If you want, I can also give you a “dishwasher-safe vs unsafe” quick cheat sheet so you can sort kitchen items in seconds.
