There's this all natural flea repellent I got from walmart. I tried it because it contained no chemicals only spices including cinnamon, nutmeg, eucalyptus and others. I forgot the exact name though. I'll post it when I get a new one. It's quite effective and I haven't really had a big problem with fleas. Being natural and all also makes a big difference.
Natural is really the way to go these days, it's more healthy and economical too.
I learned this from a friend. Just add a small cup of apple cider vinegar or any other vinegar to the drinking water. There wasn't really a time when my dogs had to suffer tick and flea infestation during any season even though they are always playing outside.
Try Advantix. Our vet said aside from killing fleas and ticks, it can also repel them. We live near an area with a considerable deer population and we had to have our dogs vaccinated against Lyme Disease.