The only thing I have found to work on my dogs and on my clients dogs is comfortis. You have to get it from your vet. I would like to recommend lone Star vet. Dr. Bryant is great and the first office visit is free. (281) 812-0257. If you use them tell them Crystal from Trendy Tailz said hello.
You can go online; do a seach on yahoo for Advantage. That works the best. Some of these products can have serious or deadly complications. We have used Advantage for years and never had a problem with fleas.