The first thing to point out that your hamster will generally designate one or two areas of its cage for a toilet. If you can change the bedding material in these areas regularly, every couple of days, you should dramatically cut down on the smells that may come from a dirty hamster cage and also prolong the period between full cage cleans.
How often should a hamster cage be cleaned out depends on how dirty they get from day to day, but you do need to ensure that stale food and droppings are removed regularly. A full clean of the hamster cage once a week is recommended.
You should never really have to bathe your hamster. Washing them is not good for their fur as the water removes the natural oils from the fur, which can make them unwell. Chinchilla sand can help keep the coat in good condition, but there may be times when you feel you have to wash your hamster. These should only be in exceptional circumstances, for example if there is something on the fur that may be toxic of harmful to your hamster if ingested (as they lick the fur to clean it). If there is a substance that needs to be removed from the fur you should consider if it is possible to cut it away, or brush it out. If this is not possible or the substance is something like paint or something very sticky and you feel forced to wet your hamster then do so very carefully with a small amount of warm water, keeping it away from the nose, mouth ears and eyes. When clean, dry your hamster very gently with a towel and if possible with a hair drier on a low setting held far away from the hamster. Make sure your hamster is completely dry before returning it to its cage so that the bedding does not stick to the fur.
One thing to consider is that if there is a bad smell coming from your hamster it may be because it is sick and the droppings are not firm, in this case you should take your pet to the vet to be checked over.
If you regularly clean and disinfect your hamster cage and remove droppings and old food as recommended above, you should easily maintain a clean, healthy and sweet smelling home for you and your hamster.
