Hi Jodie. I know this is months later, but I just came across your question, as I was looking up treatment for fleas on hamsters. As one answer you got says, you definitely can see fleas if your hamsters have them. Our hamster has fleas. Poor little thing. It was a neglected, unwanted pet we only got yesterday. The cage was infested with fleas. Farm cats near the cage - she's from a farm house - won't have helped Honey (that's what we've named her), but I believe the source of the fleas was her bedding. They used dusty, dirty wood shavings, housed in a shed where other animals are nearby. I scrubbed out her cage and put loads of torn up paper towels in there, but she still has some fleas in her fur. I shall get some 'spot on' tonight. Apart from a course of flea treatments, you need to treat areas where your pets have been and my extra main suggestion here is to check how clean the wood shavings you buy are or use an alternative. As your question was 7 months ago, I'm sure you got it sorted and hope all's well. :O)