My dad told us we need to wash tuna cans before opening them because canned food (at least tuna) is imported on ships and rats really like to "take a trip" on these ships, too. They touch those cans and thus contaminate them.

Do I really need to wash the tuna can with soap before opening it?

I feel like it is closed very tightly but, maybe for the sake of the smallest chance the tuna will touch the can.

I mean, he is not wrong with the rats on ships part, and it is also logical, and if not then for the sake of the smallest chance that arat got on board.

  • If that's the case you should wash your hands after handling the can.
    – Schwern
    Mar 4, 2021 at 6:38
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    Welcome to Skeptics! For this question to be on topic for this community, the claim in question needs to be widely believed. Can you demonstrate that there is a substantial amount of people who believe this? And are you skeptical about the fact that rats contanimate the cargo or that the contanimation is so bad that it requires cleaning? Mar 4, 2021 at 9:55
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    If the can has been in your kitchen cupboard a while, and is covered in dust, then wash it. Who knows what else it picked up in your house? Probably far more than it picked up on the ship!
    – GEdgar
    Mar 4, 2021 at 13:35
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    I never thought about this, but it makes me glad that i always rinse them due to dust.
    – Tanath
    Mar 10, 2021 at 21:02
  • The cans aren't piled on ships loose, where a rat can touch them, you know. They are boxed at least.
    – user8356
    Mar 23, 2021 at 14:59

1 Answer 1


It's not a bad idea, but tuna cans, and most other cans, are packed in boxes or wrapped in plastic at the production line and not opened until they reach the store.

The greater concern is probably all the humans who handled the can. Humans who carry disease communicable to other humans. And it isn't limited to tuna. Wash your hands.

This seems to be a twist on rat urine and soda cans "scarelore" (what a great term) accompanied by grisly consequences.

Whenever you buy a can of coke or whatever, please make sure that you wash the top with running water and soap or if not available drink with a straw.

A family friend’s friend died after drinking a can of soda! Apparently, she didn’t clean the top before drinking from the can. The top was encrusted with dried rat’s urine which is toxic and obviously lethal!!!!!

While rat urine does carry diseases like leptospirosis and hantavirus, they are rare in the western world.

  • Well, there might be rats at the store where you bought the can. Or where you stored the can prior to opening. ;-) But I agree that those on the ship or the truck are unlikely to be an issue.
    – DevSolar
    Apr 6, 2021 at 16:33
  • @DevSolar If you suspect there are rats at the store, wash everything. And find another store.
    – Schwern
    Apr 6, 2021 at 17:49
  • Not as rare as you might think, not even in first-world supermarkets. But we have to take into account small stores in poorer places as well...
    – DevSolar
    Apr 6, 2021 at 23:15

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