Your lunch box probably can't go in the microwave.

Your lunch box probably can’t go in the microwave — most lunch containers are never tested for it.

The only ones that are safe are the ones that literally say “microwave-safe” on the bottom. If it doesn’t say that, don’t assume. Unmarked plastic warps, melts, or leaches. Metal things — thermoses, tins, old-school lunch pails — will spark and can damage the microwave. And insulated lunch bags? Never. Those go nowhere near the microwave.

The sneaky part is the lid. A lot of containers have a microwave-safe base but a lid that isn’t, especially if that lid has a rubber seal. Pop the lid off before reheating, and vent anything that’s sealed shut.

If you’re unsure, grab a plate or bowl you know is safe. It’s not a hassle, it’s just lunch. A plate is cheaper than a new lunch box.