Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Update after 3months

I have used this product for three months straight and the first couple of days it works, killing all of the fleas. However, after that it completely quits working. It does not continue to kill the fleas all month long as promised. A few days after the application I will begin to see fleas pop up again on my dog. I need something that kills the eggs and keeps working all month. I am going to try Frontline to see if I have better luck there.