I work as a veterinary assistant and have talked with representatives for
both Frontline and Advantage.  Both products work in a similar fashion;
they are topical oils that are applied on the back of the neck, the oil
then mixes with natural body oil and spreads all over the skin of the
animal.  As the animal sheds skin cells, the topical oil is also shed.
Therefore, the animal thoroughly treats the areas around the house most
commonly infested with fleas, the areas where the animal spends the most
time.  Incidentally, the whole house gets treated, at least lightly, as
the animal sheds skin cells all over the house.  The active ingredient in
Advantage is a pesticide which is used on fruits and vegetables intended
for human consumption, so it is pretty safe.  Frontline uses a pesticide
which is equally as safe.  We very rarely have to suggest the use of other
pesticides, such as sprays, except in cases of extremely severe
infestation.
 
Erica
Snoball, the dog
Ripley, Max, and Jinx, the kitties
Fitz, Honey, and Buster, the ferrets
[Posted in FML issue 3543]