
I use advantage, advocate mostly but swapping in some frontline and fripoline occasionally. For the house I use indorex spray once a year.
What breed is your dog? Some breeds with the mdr1 gene like collies can have problems with the majority of stuff that contains ivermectin.
Don't feel bad, dogs pick these things up,could have come from a walk, dog event, a friend's dog or even at the groomers. I know of a groomer who takes her own dogs in while she works even when they were covered in fleas.