Plastic lunch boxes are usually not microwave-safe

If your plastic lunch box doesn’t have a microwave-safe symbol on the bottom, don’t put it in the microwave.

Flip the container over and look for the symbol: either a little microwave icon or those squiggly lines that are supposed to represent heat waves. If it’s not there, the plastic can warp, melt, or leach chemicals into your food — and you won’t know until it’s too late.

Here’s the thing people miss: even the containers labeled microwave-safe have limits. They’re tested for normal reheating, not for blasting leftover curry for five minutes straight. High-fat and high-sugar foods get way hotter than water does, and that can break down plastics that would otherwise be fine. Also, the lids are almost always the weak point. The base might be marked safe, but the lid won’t be. Take it off before heating.

Honestly, the move is to reheat in a glass or ceramic container instead. Glass won’t leach anything and doesn’t stain from tomato sauce. The only downside is the extra weight — which is why the plastic one is in your bag in the first place. I get it. But food safety is not where you save a few ounces.

If you do use the plastic one, keep the power lower, heat in short bursts, and stop if the container feels hot to the touch after. But really, just microwave in glass and transfer to plastic afterwards. This is one of those “rules” that’s actually worth following.