Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Totally ineffective

This is the second year I've tried Frontline for my two cats. I should have learned from experience, but hope springs eternal. This expensive product had no effect at all on the cats' flea problem. None. This appears to be a growing problem; perhaps the fleas have developed immunity to the chemical in this medication. Will not be buying Frontline again, until I hear that it has been improved.