Three things you should never wash in a dishwasher — the last one is the most common

The dishwasher has become a household staple, offering convenience and efficiency in modern kitchens. But according to experts, many users are unknowingly damaging their kitchenware — and even the dishwasher itself — by placing certain items inside that should never be washed in the machine. These common mistakes can shorten the life of utensils and reduce overall cleaning performance.

In a recent guide published by appliance specialists and household safety advisors, three items were highlighted as frequent offenders. While some might seem harmless, each poses unique risks when exposed to the high heat, moisture, and detergents inside a dishwasher. The full breakdown was featured by Italian outlet Tutto Notizie.

First on the list are chef knives or precision blades. Despite being made of stainless steel, these tools suffer greatly in a dishwasher. The heat and harsh detergent dull the blade rapidly, while the vibration during wash cycles can cause tiny chips or fractures along the edge. Professional chefs consistently recommend hand-washing knives and drying them immediately to preserve sharpness and hygiene.

The second item is lightweight plastic containers, particularly those not explicitly labeled as dishwasher-safe. Under high temperatures, these plastics can warp, melt slightly, or leach chemicals. Even sturdier plastics may get damaged if placed too close to the dishwasher’s heating element — usually on the lower rack — and can clog the system if they break apart mid-cycle.

But the most surprising — and most common — mistake involves wooden cutting boards. Many people toss them in the dishwasher thinking it’s convenient, but the wood absorbs moisture, leading to warping, cracks, and internal bacterial growth. The high heat accelerates deterioration, turning a once-reliable board into a hygiene risk.

Experts advise hand-washing wooden boards using warm water and mild soap, followed by immediate drying. Periodic conditioning with food-safe mineral oil can also help prolong the board’s life. The same advice applies to wooden utensils and handles, which are similarly vulnerable to water damage and microbial buildup.

Another issue that often arises is overloading the dishwasher or arranging items incorrectly. Stacking utensils too tightly, nesting cups, or placing pans in a way that blocks water jets can reduce cleaning efficiency and increase the risk of breakage. Following manufacturer guidelines and spacing items properly ensures better results and appliance longevity.

In the end, using a dishwasher doesn’t mean everything belongs in it. Knowing which items to exclude can protect your investment in quality kitchen tools and promote safer, more sustainable cleaning practices. Sometimes, a little handwashing goes a long way.