In reply to elcid:
> ... our two dogs which we treat with frontline spot-on it doesn't deter all ticks but we find an occasional one that has fallen off, dead but gorged, so why do ticks die on me?
You would get better tick protection for the dogs using a more modern POM-V ectoparasiticide. Also there are growing concerns about fipronil (and imidocloprid) getting into the environment, not just from agricultural use, but also from pets with many tons of product estimated in the environment from dogs and cats, so there are other good reasons for considering alternatives