There has been a new warning issued regarding some of the spot flea and tick pet treatments. I've stopped using them and reverted back to a collar when in the field.
http://www.epa.gov/pesticides/health/petproductseval.html
This is what bothers me about this market. People assume that because it's in the grocery store, it's safer than what you can get at the vet's.
Let me assure you, NOTHING is further from the truth. Modern chemistry is far more insect specific than the old pyrethroids they sell in the pet food aisle. And I like to call pyrethroids "caticides" because that's exactly what happens when you give them to cats, which, startlingly, they are often labeled for. This is my industry and for the life of me I do not understand why things evolved the way they did. I would not recommend these things and would never use them on my dog. They don't work that well, first of all. Or, at least, not for long enough.
If you are on a budget and want to keep your dogs from getting ticks, I highly recommend a PrevenTic collar. They are not expensive, relatively speaking. You can get them through your vet, I think you may need an Rx to get them, but I am not 100% sure about that. They contain Amitraz, highly effective against tick bites, and can last three months. Ticks are far too nasty to risk using something that doesn't really work. We now have not only borrellia (lyme disease), but rickettsia (rocky mountain spotted fever, which is almost always fatal to dogs and often to people), ehrlichia and babesia right in NJ. Tick bites are always bad news.