Dry the silicone seal before it goes back in

Mold on silicone seals is almost always because the seal went back in wet.

The cleaning part is easy. Pop the seal out of the lid and wash it with hot soapy water. If you can already see dark spots, soak it in a 50/50 white vinegar and water mix for 15-20 minutes, then scrub with a soft brush. Baking soda paste works too if the vinegar smell bothers you.

The part everyone skips is drying. Silicone is porous enough to hold moisture in those little grooves, and the lid traps it there. So after washing, let the seal and the lid channel air dry completely — like, fully bone dry — before you snap it back together. If you’re in a hurry, wipe it down with a paper towel and leave the lid open for an hour.

Also worth doing: don’t store the lunch box sealed shut when it’s empty. Leave the lid cracked or store it upside down so air gets in. That alone prevents most mold problems.

The five extra seconds of drying saves you a scrubbing session later.