Hot vinegar soak kills mold in lunch box seams.

The fastest way to handle mold in lunch box seams is a soak in hot vinegar, a scrub with an old toothbrush, and a thorough drying.

First, empty the box and wipe out any loose crumbs. Then mix about one part white vinegar with three parts hot water and fill or soak the seams. Let it sit for 10–15 minutes — that’s enough time to kill most mold without harsh bleach fumes.

Now the toothbrush. Dip it in the vinegar solution and scrub right along the seam, getting into all the little grooves. Work it in, rinse the box with clean water, and then dry it completely. Air-dry with the lid open or prop it upside down. That last step is the one people skip, and it’s exactly why the mold comes back.

If the mold is in a removable rubber gasket, take it out and soak it separately. If it still smells or shows dark spots after that, just replace the gasket — rubber soaks in mold and it’s not worth the fight.

No, you don’t need bleach. Vinegar is safer for plastic, and it gets the job done if you give it a few minutes to work.