As far my experience has lead me to believe, frontline does kill fleas without them biting, but the flea senses it's unwell, and instinctivly bites (more savagley than usual) and this then speeds it's death.
As my poor Keli has flea allergies i'm looking at the other topical flea treatments....currently investigating Program as an alternative as it specifically mentions it is useful as a treatment in flea related dermatitis..
Frontline is ok, but not the best out there.....