Some of my non tupperwear but same type boxes have white bits on the inside

[BirthdayRainbow]

They go in the dishwasher and I don't know what is causing it. I asked Lakeland as it has happened with theirs and they said they've not had it before.

Does anyone have the same, do you know what causes it and have you stopped it happening?

Photo is the worst one.

Yes I assume it is due to scuffs and dings in the interior of the plastic. They don’t scrub off. I would use up for non-food purposes personally.

Do you heat food up in them in the microwave? I know this can damage the plastic, and probably causes the plastic to leach into the food.

I thinks it's some kind of dried foodstuffs that somehow attaches to the plastic; as AnellaA said, it won't scrub off. When it happens to me, it's often chicken juice, and usually after it's been in the microwave or dishwasher.
I'm moving over to glass containers because of it, I don't think it can be hygienic.

I don't use them in the microwave and have ordered a new set for my new house for food items. That's a really good idea to keep for non food items. Thank you. I have plastic as I drop things and they bounce better than glass!

Oh, what about for pet biscuits or still a no?

I’ve had it happen to some, but only the ones that get used in the microwave regularly.

It happens to mine if I freeze food in them.

Could be acidic food degrading the surface. I don't know of a way to avoid other than using glass though.