I switched to Advantage, bathe the girls with De Flea Shampoo once a month (no chemicals), and "mist" with Adams before their evening walk which I use as much to ward off mosquitos as anything else. I feed a fish based, grain-free food with the addition of various oils (rotating salmon oil, human fish oil concentrate, flax seed oil), feed homemade treats made with loads of organic ground flax seed. Also add Springtime's "Longevity".
One of my girls used to be in constant motion - scratching, biting, licking, twitching. Poor baby! It took a year or so to get to this combination but it has eliminated about 80% of her itchies.
Frontline stopped working in this area. Had been using it for years.