There are several items that should never be put in a dishwasher.
These include:
Knives: As mentioned earlier, the heat and water of a dishwasher can damage the blade of a knife, making it dull and less effective for cutting. It is best to wash knives by hand.
Cast iron cookware: Cast iron pans and skillets should never be put in a dishwasher, as the harsh detergents can strip away the pan's seasoning and cause rust. Instead, wash cast iron cookware by hand with warm water and a mild dish soap.
Wooden utensils: Wooden spoons, cutting boards, and other utensils can become damaged in a dishwasher. The heat and water can cause the wood to warp and split, and the detergents can strip away the wood's natural oils. It is best to wash wooden utensils by hand using warm water and a mild dish soap.
Non-stick cookware: Non-stick pans and other cookware should not be put in a dishwasher, as the heat and detergents can damage the non-stick coating. This can cause the coating to flake off and potentially contaminate your food. It is best to wash non-stick cookware by hand using warm water and a mild dish soap.
Delicate or hand-painted items: Delicate or hand-painted dishes, glasses, and other items can become damaged in a dishwasher. The heat and detergents can cause the paint to fade or chip, and the high-pressure water can cause delicate items to break or shatter. It is best to wash these items by hand using warm water and a mild dish soap.