The seams are where lunch boxes go to die.

The short answer: take the liner out every time and dry it completely before you put the box back together. Seams get moldy because they stay damp, not because they’re dirty.

Wash the liner in the sink with hot water and dish soap. Use an old toothbrush on the seams — that’s where crumbs and moisture hide. If it already smells musty, add a splash of white vinegar to the water or give it a quick soak.

The drying step is the one everyone skips. Hang the liner or lay it flat somewhere with airflow and leave it overnight. Never snap it back into the box while it’s even slightly damp, because that traps moisture in the seam and you’re back to square one.

Make it a same-day habit: wash it when you get home, not in the morning. If mold has already taken hold, wash with a dilute bleach solution (about a tablespoon per quart of water), rinse well, and dry it in the sun — sunlight kills mold spores too.

Future sandwiches will thank you.