The bottom rack will melt your lunch box.

Yes, you can put it in the dishwasher, but “top-rack only” is not a suggestion — bottom-rack heat will warp or melt the plastic.

The reason is simple: the heating element is at the bottom. On the top rack, your lunch box is far enough away to stay under the plastic’s softening point. On the bottom, it’s sitting right next to the heat source. That’s how you get a bent lid, a ruined silicone seal, or a plastic-y smell that never really goes away.

Also, those little airtight containers use gaskets to keep leaks in check. High heat breaks down the rubber over time, so even if the plastic doesn’t visibly melt, the seal will eventually stop sealing. Then you get soup in your backpack. Not fun.

If you’re in a hurry, you can do top-rack. But hand-washing is still gentler and keeps the gasket alive longer. Just don’t get creative with the placement.

Your future lunch — and your bag — will thank you.