Your lunch box needs a weekly deep clean.

Deep-clean your lunch box at least once a week to keep mold from ever getting a foothold.

Daily wiping with a cloth is fine for crumbs, but it misses the real problem: moisture and food residue hiding in corners, under the latch, along the sealing edge. That’s exactly where mold spores land and start colonizing. A week is about how long it takes for things to go from “a little smelly” to “green spots in the lid hinge.”

The actual cleaning is boring but easy: hot soapy water, a scrub brush for the crevices, and then—this is the important part—let it air dry completely before closing it. Mold loves damp. If you’re someone who packs wet foods like fruit or yogurt, consider giving it a quick mid-week rinse too.

And trust your nose. If you notice a smell, you’re already late. Don’t just spray it with sanitizer and hope. Do the real wash.

Future you doesn’t want to discover a science project on a Tuesday morning.