Comfortis was tested for 90 days on dogs and the good news is, no one died. As long as the poor lab dogs don't die, then the product is considered safe to release on the market. Very sad. The studies done on rats (
http://toxsci.oxford...t/full/67/1/144) over a longer period of time came up with very scary results (the doses they use in the rat studies are higher, but they do show the potential dangers of the chemical)...
I currently use Frontline on Zoey with no problem or side effects that I know about or have noticed, but with all the sudden bad press and recent spikes in severe reactions from spot on treatments I'm planning on trying some natural remedies to see how they work out. I heard really good things about cedar oil and specifically about Dr. Ben's personal insect repellent cedar oil, which is fully diluted in a natural safe mineral solution.