[header] How to get rid of fleas on rats [title] Observe if your rat is scratching more than normal. [step] Often a rat will scratch a flea infested part of its body more frequently and often quite vigorously. This area can become irritated, red, or inflamed from scratching and from fleas feeding on your rat's skin. 
[substeps] Missing patches of fur or red scabs is a good indication that something is irritating your rat's skin even if you don't see them scratching. Fleas like to hide in densely covered areas of animals.