**8 Things You Absolutely Should Not Put in a Dishwasher **(And Why)

It is incredibly convenient to use a dishwasher after preparing a hearty meal. This modern kitchen appliance is truly a wonderful time-saver that helps minimize the effort needed to tidy up your kitchen at the end of a long day. However, it is important to remember that not every single item in your kitchen is meant to go inside this machine.

Placing the wrong kitchenware into a dishwasher does not just run the risk of ruining your favorite items. It can also cause unexpected damage to the appliance itself, create sticky messes inside the tub, and significantly shorten the lifespan of your culinary tools.

This guide is not meant to cause unnecessary worry. Instead, it is designed to provide clear, practical information. When you understand what science and culinary professionals say about appliance safety, you can better protect your household investments and ensure your machine runs efficiently for a very long time. Let us take a close look at the specific items that should stay in the sink, along with the proper ways to maintain them.

The Golden Rule: When you are not completely sure if an item can go in the machine, it is always best to look closely at the manufacturer’s label. If you see the words “Hand Wash Only,” it is wise to trust that advice. The intense heat levels and the high water pressure inside a dishwasher are much more aggressive than a gentle wash by hand in the sink.

1. Sharp Knives and Wooden Utensils

Let us start with a piece of information that might surprise quite a few people. Not too long ago, celebrity chef Ina Garten shared a photograph on her Instagram account, and it revealed something unexpected. She actually had her kitchen knives loaded right into her dishwasher! You might be wondering, “What’s the big deal?”

The reality of the situation is that the high water pressure inside the machine causes knives to bump repeatedly against other items in the dish rack. This constant friction dulls the sharp edge of the blade incredibly quickly.

On top of that, the intense heat levels and the strong chemicals found in automated dish detergents can cause wooden handles to split, warp, or completely loosen from the metal blade. There is also a physical safety risk to think about, as reaching blindly into a rack filled with hidden, sharp blades can easily lead to an accidental injury.

Proper Care Instructions

It is best to wash your knives and wooden spoons immediately after you finish using them by using warm water and mild liquid soap. Dry them thoroughly right away with a clean towel to stop rust from forming, which is especially important for carbon steel tools.

Store your blades safely inside a dedicated knife block or along a secure magnetic strip. Every once in a while, take a moment to rub a bit of food-safe mineral oil onto your wooden handles to keep the wood from drying out. Even if a manufacturer claims a knife is “dishwasher safe,” opting to hand wash will keep that edge razor-sharp for a much longer period.

2. Delicate Crystal and Fine China

If you own beautiful crystal stemware or elegant fine china, these pieces truly deserve the highest level of care.

The powerful water jets inside an appliance can easily cause fragile glassware to chip or completely shatter if it knocks against nearby dishes. Furthermore, strong detergents combined with intense heat can permanently etch the delicate surface of crystal. This creates a cloudy appearance that cannot be fixed, no matter how much you try to polish it afterward. To make matters worse, any beautiful gold or silver metallic trim on the edges of your fine china will likely fade, peel, or wash away entirely over time.

Proper Care Instructions

To clean these items safely, place a soft towel at the bottom of a plastic basin or your sink to prevent any accidental slipping or chipping. Wash each piece gently using a mild dish soap mixed with lukewarm water.

Rinse them thoroughly and allow them to air dry completely on a safe drying rack, or wipe them down carefully with a lint-free towel. When you store them away, make sure you never stack heavy objects on top of these delicate items.

3. Cast Iron Cookware

Cast iron skillets are widely considered the ultimate workhorses of the kitchen, but they absolutely despise the automated environment of a dishwasher.

The heavy-duty detergents and high heat cycles will completely strip away the carefully built-up layer of polymerized oil. This layer is commonly known as the seasoning, and it is exactly what gives cast iron its natural, non-stick quality.

When this protective barrier is stripped away, the bare iron will rust very quickly when it comes into contact with moisture and air. If a cast iron pan is put through repeated appliance cycles over time, the surface of the metal will degrade severely.

Proper Care Instructions

You should always wash cast iron by hand using hot water and a stiff-bristled cleaning brush. In most cases, you do not even need to use soap.

Once the pan is clean, dry it completely by placing it on your stovetop over low heat for a few minutes. Afterward, rub a very light coating of cooking oil over the surface while it is still warm to maintain that beautiful non-stick finish. Finally, make sure you never leave cast iron to soak in water for long stretches of time.

4. Nonstick Cookware

It might seem a bit backwards at first, especially since nonstick frying pans are specifically designed to make cleanup easy, but they really ought to stay far away from the dishwasher.

The aggressive chemical formulas of modern detergents paired with extreme temperatures work to break down the specialized nonstick coating, such as PTFE or Teflon. This causes the coating to flake off into food and lose its effectiveness entirely. This accelerates the general wear and tear of the pan, meaning you will find yourself forced to buy expensive replacement cookware much sooner than expected.

Proper Care Instructions

Always wash your nonstick pans by hand with a soft, non-abrasive sponge and a bit of mild dish soap. Be sure to avoid tough cleaning tools like steel wool or metallic scouring pads.

It is also highly important to let the pan cool down completely to room temperature before you introduce it to water, as sudden temperature changes can warp the metal. While some modern ceramic-coated pans advertise themselves as dishwasher safe, washing them by hand will always extend their usable lifespan.

5. Anything with Adhesive Labels

Many of us have experienced the annoyance of trying to scrape a baked-on sticker off a jar or plate after it has already gone through a dishwasher cycle. It can be a real hassle to deal with.

When paper labels are exposed to hot water and heat, they quickly disintegrate. This process leaves behind a stubborn, sticky residue on the item itself and all over the inside of the machine.

Even worse, the tiny fragments of paper and melted adhesive glue can easily pass into the dishwasher’s filtration system, causing clogs and drastically reducing how well the machine cleans your dishes. In the end, you will likely spend far more time trying to clean out the sticky mess than the time you initially hoped to save by using the appliance.

Proper Care Instructions

Make it a strict rule to remove all store labels, price tags, and stickers before you place any item into the machine. If a label is stuck fast, soak the item in a basin of warm, soapy water to loosen the adhesive backing. You can then gently use a flat scraper or a safe blade to slide the leftover glue right off the surface.

6. Insulated Travel Mugs and Thermoses

Insulated travel cups are fantastic tools for keeping your morning coffee hot or your water ice-cold for hours, but a dishwasher can completely ruin how they function.

The intense heat inside the machine can destroy the delicate vacuum seal that exists between the double walls of the container. Once that seal is broken, the travel mug loses its ability to retain temperature properly.

In addition to that issue, plastic lids and rubber sealing rings can warp or break down from the heat, which inevitably leads to messy spills and leaks. The harsh detergents can also leave a stubborn chemical odor or taste trapped inside the container’s interior.

Proper Care Instructions

Wash the main body of the thermos and the lid by hand using warm water and dish soap. A long bottle brush is an excellent tool to help you reach all the way down to the bottom of the container.

Once clean, let the pieces air dry completely with the lid left off, which helps prevent the growth of mold or mildew. Always double-check the specific instructions provided by the manufacturer, but washing by hand is universally the safest option for these items.

7. Copper Cookware

Copper pots and pans look absolutely beautiful when displayed in a kitchen, but they require a high level of specialized care to keep them looking that way.

The strong detergents and intense heat cycles of an appliance will quickly tarnish the gorgeous metallic finish, causing it to look dark, dull, and spotty. A standard machine simply cannot provide the gentle, specific care needed to preserve that highly polished shine. Furthermore, certain types of dish soaps can actually trigger a chemical reaction with the copper metal, leading to permanent pitting or surface corrosion.

Proper Care Instructions

Clean your copper pieces by hand using mild dish soap and warm water, and make sure to dry them off immediately with a towel to prevent water spots from forming. To keep that beautiful shine alive, polish the metal regularly using a commercial cleaner made specifically for copper, or create a simple homemade paste using a mixture of fresh lemon juice and regular table salt.

8. Old or Valuable China

If you are lucky enough to own precious family heirloom china or antique dishes that feature delicate, hand-painted artwork, you should keep them far away from the automated wash.

Repeatedly exposing these items to hot water and aggressive detergents will inevitably cause those beautiful, historic designs to fade away. Older porcelain and china are also much more brittle than modern dishware, meaning the high water pressure inside the machine makes them highly susceptible to chipping. Additionally, the rapid shift in temperature during the cycle can cause thermal shock, which creates microscopic cracks across antique pieces.

Proper Care Instructions

Wash these pieces with extreme care by hand using lukewarm water, a mild dish soap, and a very soft cloth or sponge. Stay completely away from any abrasive cleaning pads. Dry them gently with a soft, plush towel, and store them securely in a cabinet where they will not accidentally bump into one another.

Helpful Guide: Common Dishwasher Mistakes to Avoid

Learning which kitchen items need to be washed by hand is only half the battle. To ensure you get the absolute best performance out of your appliance, try your best to avoid these frequent missteps:

• Overloading the Racks: Cramming too many dishes into the machine blocks the path of the water spray. This leaves items looking dirty. Always load your dishes according to the official manual guidelines and leave plenty of open space between items so water can circulate freely.

• Pre-Rinsing Too Much: Modern dish soaps actually require food particles to activate properly and do their job. Instead of washing the dishes completely in the sink beforehand, simply scrape the large chunks of food into the trash and let your detergent handle the rest.

• Using the Wrong Soap: Pouring regular liquid hand-washing dish soap into the appliance dispenser will cause a massive, sudsy overflow all over your kitchen floor. Always use high-quality dishwasher pods, gels, or powders designed specifically for the machine.

• Neglecting the Filter: A filter that is clogged up with old food scraps will severely reduce the overall cleaning power of your machine. Make it a habit to remove and clean out the filter once a month according to your manufacturer’s instructions.

• Skipping the Rinse Aid: Forgetting to use rinse aid often results in annoying water spots and a dull film developing over your glassware. Keep the designated rinse aid dispenser filled up regularly.

Pro Tip: To keep the interior of your appliance clean and completely free of unpleasant odors, place a dishwasher-safe cup filled with white vinegar on the top rack of an entirely empty machine and run a hot cycle once every month.