Things You Absolutely Should Not Put in a Dishwasher

Common Mistakes That Can Ruin Your Kitchen Items—and Your Dishwasher

Introduction: The Dishwasher Is Helpful, Not Magical

The dishwasher is one of the most convenient appliances in the modern kitchen. With the push of a button, it promises to clean, sanitize, and dry our dishes while we move on with our day. Over time, it becomes tempting to put everything in there—after all, if it fits, it should be fine… right?

Unfortunately, that assumption leads to countless ruined kitchen tools, dulled blades, warped cookware, cracked finishes, and even dishwasher damage.

The truth is simple:
Not everything is dishwasher-safe—even if it looks sturdy.

In this guide, we’ll walk through the most common items people mistakenly put in the dishwasher, explain why they don’t belong there, and help you protect both your kitchen gear and your appliance.

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Why Some Items Don’t Belong in the Dishwasher

Dishwashers clean using:

• Extremely hot water

• Strong alkaline detergents

• High-pressure spray

• Extended drying heat

While perfect for plates and glassware, this environment is harsh on certain materials. Heat can warp, detergents can corrode, and moisture can damage finishes.

Knowing what to keep out can save you money—and frustration.

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1. Sharp Knives

This is one of the most common dishwasher mistakes.

Why You Shouldn’t:

• High heat dulls blades

• Detergents corrode metal edges

• Knives can knock against other items

• Risk of injury when unloading

Even “dishwasher-safe” knives lose sharpness faster when machine-washed.

Best Practice:

Wash knives by hand immediately after use, dry them, and store properly.

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2. Wooden Items (Cutting Boards, Utensils, Bowls)

Wood and dishwashers do not mix.

What Happens:

• Wood absorbs water

• Expands and contracts

• Cracks, splits, or warps

• Loses natural oils

Repeated dishwasher cycles can permanently damage wooden items.

Items to Avoid:

• Cutting boards

• Wooden spoons

• Salad bowls

• Rolling pins

Best Practice:

Hand wash quickly, dry immediately, and occasionally oil with food-grade mineral oil.

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3. Cast Iron Cookware

Cast iron is built to last—but not in a dishwasher.

Why It’s a Problem:

• Removes seasoning

• Causes rust

• Harsh detergents strip protective oil

Even one dishwasher cycle can undo years of careful seasoning.

Best Practice:

Clean cast iron with warm water and a brush, dry thoroughly, and re-oil lightly.

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4. Nonstick Pans

Many nonstick pans claim to be dishwasher-safe—but that doesn’t mean it’s wise.

Dishwasher Damage Includes:

• Breakdown of nonstick coating

• Reduced lifespan

• Peeling over time

Heat and detergent accelerate wear dramatically.

Best Practice:

Hand wash gently with a soft sponge to preserve the coating.

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5. Aluminum Cookware and Utensils

Aluminum reacts poorly to dishwasher detergent.

What Can Happen:

• Oxidation

• Discoloration

• Dull, chalky residue

This includes aluminum baking sheets, pots, and some utensils.

Best Practice:

Hand wash aluminum items to maintain appearance and performance.

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6. Copper Pots and Pans

Copper is prized for its beauty—but dishwashers destroy that shine.

Dishwasher Effects:

• Tarnishing

• Pitting

• Permanent dullness

Even copper-plated items can be damaged.

Best Practice:

Wash by hand and polish occasionally to maintain luster.

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7. Crystal Glassware

Fine crystal is far more delicate than regular glass.

Risks:

• Clouding

• Etching

• Cracking from temperature changes

High-pressure water can also cause pieces to bump and chip.

Best Practice:

Wash crystal by hand with warm water and mild soap.

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8. Insulated Travel Mugs and Tumblers

Double-walled insulated cups often trap water.

Dishwasher Problems:

• Water gets trapped between layers

• Insulation effectiveness decreases

• Seals can fail

This applies to many stainless steel tumblers and thermal mugs.

Best Practice:

Check manufacturer instructions; when in doubt, hand wash.

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9. Plastic Items Not Labeled Dishwasher-Safe

Heat is plastic’s enemy.

What Can Go Wrong:

• Warping

• Melting

• Chemical leaching

• Misshapen lids

Thin plastics are especially vulnerable.

Best Practice:

Only place plastics clearly marked “top rack dishwasher safe” in the dishwasher.

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10. Gold-Trimmed or Hand-Painted Dishes

Decorative finishes are often fragile.

Dishwasher Damage:

• Fading

• Peeling

• Cracking

Detergents are particularly harsh on metallic accents.

Best Practice:

Hand wash decorative items to preserve their design.

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11. Cheese Graters and Fine Strainers

These seem dishwasher-friendly—but aren’t ideal.

Why:

• Food particles get stuck

• Can rust or dull

• Fine mesh can warp

Best Practice:

Rinse immediately after use and hand wash thoroughly.

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12. Pressure Cooker Lids

Pressure cooker lids contain valves and seals.

Dishwasher Risks:

• Water trapped in mechanisms

• Damaged seals

• Reduced pressure performance

Best Practice:

Hand wash lids carefully and air dry completely.

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13. Baby Bottles and Nipples (Not Dishwasher-Safe Types)

While some baby items are dishwasher-safe, others are not.

Risks:

• Deformation

• Micro-cracks

• Reduced sanitation effectiveness

Always follow manufacturer guidelines.

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14. Graters, Zesters, and Microplanes

These tools dull quickly in dishwashers.

Problems:

• Dulling blades

• Food debris stuck in teeth

• Rust development

Best Practice:

Rinse immediately and hand wash.

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15. Anything With Stickers or Labels

Dishwashers don’t remove labels cleanly.

Results:

• Sticky residue

• Clogged filters

• Gunk buildup inside dishwasher

Always remove labels before washing.

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16. Appliances and Electronic Components

This may seem obvious—but accidents happen.

Never Put In:

• Blender bases

• Food processor motors

• Electric kettle bases

Even a quick rinse can destroy electronics.

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Why This Matters More Than You Think

Putting the wrong items in the dishwasher doesn’t just damage them—it can also:

• Clog filters

• Damage spray arms

• Shorten appliance lifespan

• Reduce cleaning effectiveness

Protecting your dishwasher protects everything else.

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How to Know If Something Is Dishwasher-Safe

Check for:

• Manufacturer labels

• Symbols on the bottom

• Instruction manuals

• Official brand websites

When unsure, hand washing is always safer.

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A Simple Rule to Remember

If an item is:

• Sharp

• Wooden

• Nonstick

• Decorative

• Insulated

• Handcrafted

👉 It probably doesn’t belong in the dishwasher.

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Final Thoughts: Convenience With Care

Dishwashers are amazing tools—but they’re not one-size-fits-all.

A little extra effort at the sink can:

• Extend the life of your kitchen tools

• Keep your dishwasher running smoothly

• Preserve items you love

Knowing what not to load is just as important as knowing how to load it.

Sometimes, the smartest kitchen habit is choosing when not to press start.