Many items are technically washable in a dishwasher, but some can be damaged—or damage the dishwasher itself. Here are 8 things you should generally avoid putting in the dishwasher and why:
- Sharp knives
- Dishwasher detergents and the jostling during a cycle can dull the blade.
- Hand-washing helps keep knives sharp and protects the edge.
- Cast iron cookware
- Dishwasher detergent and prolonged exposure to water can strip the seasoning and promote rust.
- Wash by hand, dry immediately, and lightly oil if needed.
- Wooden utensils and cutting boards
- Heat and moisture can cause wood to warp, crack, or split.
- Hand-wash and dry thoroughly.
- Nonstick cookware (some types)
- While many newer pans are labeled dishwasher-safe, repeated dishwasher cycles can shorten the life of the nonstick coating.
- Check the manufacturer’s instructions; hand-washing is often gentler.
- Insulated travel mugs or bottles (unless labeled dishwasher-safe)
- High heat can damage the vacuum seal, reducing insulation.
- Follow the manufacturer’s care instructions.
- Crystal and delicate glassware
- High temperatures and strong detergents can cause clouding, scratching, or breakage.
- Wash by hand with mild soap.
- Copper, brass, and some aluminum items
- These metals may tarnish, discolor, or react with dishwasher detergent.
- Hand-washing helps preserve their finish.
- Items with glued-on parts or labels
- Heat and water can weaken adhesives, causing handles, decorations, or labels to come loose.
Bonus: Check before you wash
Many modern kitchen items are designed to be dishwasher-safe. When in doubt:
- Look for a “dishwasher-safe” symbol or care instructions.
- If the item is expensive, antique, or has a specialty finish, hand-washing is usually the safer option.
Bottom line: The dishwasher is convenient, but hand-washing is the better choice for items that are sharp, made of wood or cast iron, insulated, delicate, or have finishes or adhesives that can be damaged by heat and detergent.
