It's commonly believed that metal bar-biting is a natural, and even a beneficial part of a hamster's life in a cage. This is not the case - and cage-biting can actually be detrimental to the animal's health.
If they regularly gnaw at the bars, hamsters can damage or even break their teeth. The habit can also lead to mouth and facial injuries, often through a condition known as bar-rub. Metal bars are not good for a hamster’s teeth - they’re far too hard, and will push the teeth out of their normal alignment.

Bar rub is one of the hazards of cage bar-chewing
A hamster that keeps biting the bars of its cage is lacking healthier forms of mental and physical simulation. The habit can also result from a hamster who lacks space, or who has overgrown teeth.
Hamsters are generally good at entertaining themselves. However, it is recommended that they are taken from their cage for some human interaction, and/or a session in the exercise ball, at least once every 24 hours. If you catch the hamster chewing the bars, intervene by taking it from the cage for some play time. You could then try increasing the frequency of these play sessions - again, a hamster exercise ball will take the pressure off you as the sole provider of fun!
if this fails to reduce the bar-chewing, there may be some issue with the hamster's teeth. If they are overgrown he might be driven to gnaw on the metal.
Give Your Hamster Something To Chew
Hamsters love to chew, so provide something good to chew on, to remove the temptation of the cage bars. Hamsters' teeth are constantly growing, and they need hard food and wooden chews in order to keep these teeth down to size. The cage bars are often a last resort, if there’s nothing else to chew on. If you feed your pet hamster pellets (which are quite soft), try changing to solid dry foods instead - that will help wear down the teeth.
Is There A Problem With Your Hamster Cage?
If you’ve tried the options mentioned above, with no good result, the problem may lie with the cage itself. Your hamster may simply be trying to escape from an enclosure that's too small. In the absence of an obvious way out, the only thing they can do is attempt to gnaw their way out. This problem is commoner than you might think, as cages intended for mice are often used in the mistaken belief that they are suitable for hamsters.
There are plenty of suitable cages available, many of them lacking bars altogether. A custom-made enclosure such as the Qute is ideal.
Brenda;, 23 February 2023
Please do not advise people to put their hamster in a ball. These are very dangerous. They do not provide enough ventilation, they are stressful for hamsters, and there have been numerous foot & toe injuries, sometimes with toes getting ripped off. These are very very dangerous.