OK, I think we need to get a definition of flees here. Where I am all the flees we get are animal flees. This type of insect can not survive without a host for more then a few hours. So, the type of flee I'm used to only lives on dogs and cats. In fact the can't even live on humans for more then a few hours. If you get one on you it will try to get away and find another dog. I've had dogs with flees and this is how it works. (At least around here). Now, there may be another type of flee, or another small insect that some people call a flee. We just don't have them around here.
If your dog has flees you can treat it with a chemical where you just put a little spot of this on the dogs back. If gets into the dogs blood steam and all the flees die. I'm not really happy with the fact that I feal like I'm poisoning my dog with this stuff. The only dog I had with flees lived for 14 years so this stuff must not be so bad.