Silicone survives. The plastic? Maybe not.

Silicone seals are usually dishwasher safe, but the rest of the lunch box might not be.

Silicone itself handles heat just fine. It’s made for it. The real issue is whatever the box is made of. If it’s a plastic container, the dishwasher’s high heat can warp it, make it cloudy, or slowly stress the lid so it no longer snaps on tight. That’s the thing that will actually ruin your lunch box — not the seal.

If it’s glass or stainless steel, you’re basically fine. Throw it on the top rack and don’t think about it. But even then, the seal will wear out faster with repeated dishwasher cycles. Dishwasher detergents are aggressive, and over time they can cause the silicone to stretch or lose its snug fit.

If it’s a cheap plastic box, hand washing is the smarter move. It takes ten seconds and saves you from a warped lid that won’t close.

Future you doesn’t want soup in their bag.