Instruct: Classify the given review as either positive or negative.
Query: Doesn't work!

I rarely completely pan a product, but I have to this time. I put Frontline on my little dog just last week, and then last night, he was again flea covered! I've bought Frontline before, and had good success with it, but for some reason, this time it's not working. I will not purchase it again, and I still have 5 tubes of it left! *sigh*