Are you sure the product you used before was "Petguard"? Is it possible that it was PetArmor? Do you know what the active ingredient is?
Also, where did you see on the Frontline website that you can apply every two weeks? The only thing I could find said not to reapply for 30 days. I would wait the 30 days.
It could be that the itching has nothing to do with fleas. I just got back from the vet today. She said this is a terrible time for environmental allergies.
Lila mit der Floppy-Ohr
Teddy the Fearless
Chaz the Spaz
Pokey - you don't know what you've got 'till it's gone
Zoey - may you catch the UPS man
Auggie -may you find the peace you never had