Most lunch boxes handle the dishwasher. The lid is the weak link.

Most lunch boxes are dishwasher-safe, but the lid often isn’t. That’s where the rubber seals, hinges, and valves live, and they take the most damage.

The easy rule: the main container — whether it’s glass, stainless steel, or a decent plastic like polypropylene (#5) — can usually go on the top rack. The lids with gaskets and locking tabs should go on the top rack too, or better yet, on the silverware basket so they don’t warp from the heating element at the bottom. If your machine has a heated dry cycle, either turn it off or use air-dry only, because that’s what kills the seals.

Stainless steel lunch boxes are the exception. Some are fine, but many have a vacuum seal or a painted exterior that doesn’t love harsh detergents and heat. Check the bottom for a “dishwasher-safe” stamp. If you don’t see one, hand wash it — that’s not me being paranoid, that’s me having ruined a perfectly good stainless thermos.

Plastic is where people get burned. If it’s flimsy or doesn’t have a resin code on the bottom, don’t trust it. And never put a plastic lunch box on the bottom rack. That’s how you get a bent lid that won’t snap shut.

The short version: container yes, lid maybe, and when in doubt, hand-wash the parts with rubber. It takes thirty seconds, and you’ll never have to argue with a soggy cheese sandwich again.