I've yet to see or hear of a dog who dropped dead from a whiff of Frontline. I don't care what decision you or anyone else makes. I just don't like fear-mongering. Let's take fipronil as an example (the active ingredient in Frontline). It is a GABA (a neurotransmitter) agonist, causing paralysis. It has a special affinity for insect GABA(A) receptors >700 times that of its affinity for mammalian GABA receptors, giving it a fairly wide margin of safety in mammals. That means that our GABA receptors are slightly different than insect GABA receptors, and it is over 700x more attracted to theirs than ours. Again, the dose makes the poison... so at very high levels you could see the same signs in dogs as in insects, but at the levels used in flea control products, there is no concern of neurotoxicosis from fipronil applied topically to dogs. Nor have I ever seen a confirmed, documented case report where someone can actually say "this happened to this specific person and this specific dog" beyond vague internet rumors of cases when the product was used topically as directed. Also, the safety and side effect evaluations on a product like fipronil is performed on laboratory dogs fed large quantities of fipronil every day in safety trials, not studies in pet animals who have been exposed to the topical product on a monthly basis. The dose makes the poison. The dose is the poison. (There's nothing inherently effective about them as far as I know, either.) Again, I don't actually care if you use Bug Off or Frontline or Bio Spot or a special rock you bought on Ebay that keeps fleas away. I just hate wooly logic and weasel words.