Most of the flea meds like Advantage are safe for puppies 8 weeks and older. Linus had a flea or two early on, probably from my yard where lots of stray cats are in and out of. He was born and brought home in the summertime, so no surprise there. You can just talk to your vet when you see him if that will make you feel better. Flea control should not overload his system. Those suckers are impossible to see on black dogs, too. Ugh!