The subject of these products makes me crazy. I hate every time I open one of these vials and administer them--but, I keep doing it between May and Nov.
Take a look at:
Compare the active ingredients of BioSpot, K9 Advantix, and Frontline Plus.
The average price per pill:
Biospot-$4, K9 Advantix-$11, Frontline Plus-$12
The question of how they actually work has always been a bone of contention for me. Follicular transference vs systemic--I find it hard to believe it doesn't penetrate the skin (and, that goes for all of them).
So, I can see why p59 came to his conclusions---if you compare ingredients. K9 Advantix and BioSpot say they repel mosquitoes (not ticks). A friend has used BioSpot for years with no problems. I've used Frontline Plus with no problems, and because of this fact, I'm hesitant to try anything new---just because you-never-know.
Honestly, when did we all start using these vials, anyway. About, 10 yrs ago, yes? Personally, I would love to hear some of the ages of your dogs, and how long they've been on these products. No matter what--it's still poison.
BTW--Anyone have a tip to recommend some natural substance, such as an non-poisonous oil, that would repel TICKS that can be rubbed lightly on the dog? I hate the ticks even going for a bite. Yes, they die with Frontline, but it still makes me uneasy.