It is advisable to bathe them once every 1 to 3 weeks.
The bathing frequency of hamsters mainly depends on the season and their living environment. Here are some specific suggestions:

The Influence of Seasons
Summer: Due to the high temperature, it is recommended to let the hamster take a bath once a week to prevent the growth of bacteria.
Winter: When the temperature is low, you can let the hamster take a bath once every 2 to 3 weeks.
Spring and Autumn: With a suitable climate, you can let the hamster take a bath once every 1 to 2 weeks.
Living Environment
If the hamster's living environment is poor, or there are a large number of hamsters and they are densely populated, you can appropriately increase the bathing frequency.
Bathing Methods
Bathing Sand: It is recommended to use special bathing sand for hamsters and avoid bathing them with water. The bathing sand can be reused 3 times before being replaced.
Precautions: Be gentle when bathing the hamster, and make sure to keep its fur dry after the bath.
Special Circumstances
If the hamster's living environment is clean and the number of hamsters is small, you can appropriately reduce the bathing frequency.
Conclusion: The bathing frequency of hamsters should be adjusted flexibly according to the season and actual situation. Generally, it is recommended to bathe them once every 1 to 3 weeks. Use bathing sand and pay attention to keeping them clean and dry.