Have lots of dog clients.  near beach/ocean there were some fleas tearing them up.  neck/back flea treatments were not working/keeping up.  this collar knocks them out shortly after they jump on.  so yes works pretty great in flea infested locations.  Retirement center standard poodle was having problems with fleas as well.  internal and external applications were not able to keep up.  this collar seems to be knocking them out.