I took my puppy to the vet for the first time after 2 days of having him. The vet suggessted using Frontline Plus on him. I bought a one month supply as his weight would soon change. I heard people warn me about using the frontline on my dog becuase they have had allergic reactions to it. I deicided to go ahead and use it on him anyway, beings the vet I went to rated it number 1. I put it between his shoulder blades and watched him carefully for the next 48 hours. The greasy looking spot dissappeared after about 48 hours and he seemed to be his happy self. I have continued to use it and we walk...