Oil, not bleach, gets tomato stains out.

Oil is the fastest way to lift a stubborn tomato sauce stain from a plastic lunch box.

The stain isn’t really “dirt.” It’s lycopene, the pigment that makes tomatoes red, and it’s dissolved in oil. Soap and water alone can’t grab it because it’s locked in a grease film. Cooking oil can. Coat the stain with vegetable or olive oil, let it sit for ten minutes, rub gently with a paper towel, then wash normally with dish soap. Most stains come right off.

For old, set-in stains, skip the scrubbing and use the sun. UV light bleaches lycopene out of plastic in a day or two of direct sunlight. It looks like magic because it basically is.

Two things to avoid: hot water, which sets the stain into the plastic, and bleach, which can yellow or cloud cheap plastic anyway.

Your lunch box might still smell vaguely of tomatoes, but at least it won’t look like a crime scene.