It could be an eye injury or some other kind of illness. If you are in doubt, then it is a good idea to take him/her to a qualified exotics vet for an exam.
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sophea (1):
my hamster always has one eye shut i keep an eye on it to make sure and if it isnt the i wipe it off with a damp warm washrag or something if that does not help i would probably take it to the vet good luck with your hamster add a comment
If the eye is tearing up, he might have just hurt it a little, and he should be fine in a few hours to a day. If he keeps his eye closed for more than two days, you should see a vet, because he might have damaged it.
my hamster always has one eye shut i keep an eye on it to make sure and if it isnt the i wipe it off with a damp warm washrag or something if that does not help i would probably take it to the vet good luck with your hamster add a comment