Rats are actually very clean animals, and if you keep their cage clean, this is rarely if ever an issue. Bathing them too frequently can actually irritate their skin.
Are Rats Clean Pets?
If you ever need to bathe your rats (which should only be if they are overly smelly, or get into something messy), Dawn Dish soap, baby shampoo, or a shampoo designed for small animals with lukewarm water works well. Be sure not to get ears, eyes, or nose wet in the bath.
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You can use the sink, or a large bowl of water for this. Some people will set their rats in the tub and carefully pour water over their backs, as some rats don’t like sitting in pools of water and can find it frightening. On the other hand, some rats love the water, and wont have any problem with bath time.
Distilled white vinegar mixed with water in a spray bottle works really well as a safe disinfectant when cleaning cages.
Make sure not to use anything like windex or other household cleaners, as these can be very dangerous to rats.