Most lunch boxes are dishwasher-safe. Bamboo is not.

Most lunch boxes are dishwasher-safe, but the lid and the lining matter more than the box itself. The bottom of a plastic or glass container will survive fine; the trouble starts with anything glued, painted, or made from wood.

Plastic containers marked with a #2, #4, or #5 recycling symbol are generally fine on the top rack. Stay away from anything that feels flimsy or looks cloudy after a wash — that’s the plastic degrading. The same goes for glass: the box is fine, but let it cool down before hitting it with hot water if it just came out of the fridge. And the rubber seal on a glass lid will eventually warp, so put the lid on the top rack or wash it by hand if you want it to stay tight.

Stainless steel lunch boxes and bottles are safe in the dishwasher, but the silicone or rubber gaskets aren’t. They’ll stretch and lose their seal after a few cycles, so if the lid is one of those twist-on with a gasket, hand-wash the lid.

Never put wooden lunch boxes, bamboo containers, or anything with a natural finish in the dishwasher. The wood swells, the finish peels, and the glue breaks down. Also, insulated lunch bags with foil lining are not dishwasher-safe, no matter what anyone says. Wipe those out with a cloth.

When in doubt, check the bottom for a symbol — or just wash it by hand. Cheap lunch boxes are easier to replace than your time nursing a warped lid.