Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Frontline Plus flea and tick control

I had been using Frontline flea control on my Yorky for sometime and never had a problem untilthis Spring and Summer. I used it faithfully every month. My groomer started telling me that she would have a flea now and then, I wasn't concerned untilthis started happening every month, more fleas. My Yorky started having allergy spots on her from the flea bites. Many dollars later, I switched toComfortis through my Vet, problem solved. I always bought my Frontline through Amazon, "I'm just sayin". I wrote Merial about my concerns, they must havethrown my letter in the trash, no response. No more Frontline for us. Something has changed and I don't think it was my dog.