*8 things you should never put in the dishwasher

That headline is a classic internet listicle hook, but unlike health scare clickbait, this one is actually doing you a massive favor. Throwing the wrong item into the dishwasher can ruin family heirlooms, warp expensive cookware, or strip away finishes in a single cycle.

1. Cast Iron Skillets

• Why: The dishwasher’s harsh water and detergent will completely strip away the seasoned oil layer that protects the iron, leaving the skillet vulnerable to rapid rust and ruining its non-stick surface.
• How to clean: Wash by hand with hot water and a stiff brush (mild soap is fine if needed), dry immediately on the stove over low heat, and rub a tiny dab of oil over the surface.

2. Wooden Cutting Boards, Bowls, and Utensils

• Why: The prolonged heat and soaking water cause wood to expand, warp, and ultimately split or crack. It also strips out the natural oils, leaving the wood dry and splintery.
• How to clean: Hand wash gently with warm soapy water, rinse, and dry immediately. Treat occasionally with food-grade mineral oil or beeswax to keep the wood conditioned.

3. Sharp Knives (Chef’s Knives, High-End Cutlery)

• Why: Bumping around against other utensils in the dishwasher dulls the razor-sharp blade edge. Furthermore, the intense heat can loosen the handles (especially if they are wood or resin), and moisture can cause rust spots.
• How to clean: Always hand wash immediately after use with warm soapy water and dry with a towel.

4. Insulated Travel Mugs and Tumblers (like Yeti or Hydro Flask)

• Why: Many double-walled insulated mugs rely on a vacuum seal to keep your drinks hot or cold. The extreme heat of a dishwasher can break that seal, rendering the insulation useless (and letting water leak inside the walls).
• How to clean: Hand wash with warm soapy water and a bottle brush.

5. Fine China and Crystal (with Gold or Silver Trim)

• Why: The harsh abrasive detergents and high-heat drying cycles will literally etch glassware, making it look permanently cloudy, and will wear away delicate metallic paint or rims.
• How to clean: Wash gently by hand in a sink lined with a soft towel to prevent chipping.

6. Non-Stick Cookware (Teflon Pans)

• Why: Even if the manufacturer says “dishwasher safe,” the aggressive detergents and high heat will degrade and pit the non-stick coating over time, causing food to stick and shortening the pan’s lifespan.
• How to clean: Let the pan cool, then hand wash with a soft sponge and mild dish soap.

7. Aluminum and Copper Cookware

• Why: Raw or un-anodized aluminum will react with harsh dishwasher detergents, causing it to oxidize, turn a dull dark gray, and leave a powdery residue. Copper will quickly lose its bright shine and tarnish severely.
• How to clean: Hand wash with mild soap. For copper, use a dedicated copper cleaner or a paste of lemon juice and salt to restore the shine.

8. Plastics That Aren’t Labeled “Top-Rack Safe” (or Any Thin Plastics)

• Why: The heating element at the bottom of a dishwasher is extremely hot. Thin plastic containers or lids placed on the bottom rack can warp, melt, or leach chemicals.
• How to clean: Always place safe plastics on the top rack (further away from the heating element) or hand wash them.

The Takeaway: If an item is wooden, sharp, insulated, cast iron, or hand-painted, it’s always safest to wash it by hand. Saving five minutes by tossing it in the machine usually costs you the item!