Here's a few things you can do.
1) If you use a spot on
Advantix has been working much better then Frontline this season. We're actually switching to selling Advantix over Frontline, because of this.
2) You can use
Yeast and Garlic as an ongoing supplement and as a natural flea repellent.
3) If you have fleas or see fleas, you can use
Best Yet Cedar Cide spray. It's an amazing product, kills on contact and is completely safe. It always promotes healing of the skin and moisturizes it. It's good to just to have a bottle, it works on just about pest you will find in your house.