SHI TZU Dog. Eucalyptus oil for Fleas? Benedryl,Is there something better?

The fleas are so bad this year, everytime I take my shi tzu outside he gets fleas. I keep giving him baths to kill the fleas. I started him on the Program flea pills last month but it doesn't seem to keep him from getting fleas that want to hang out on him. I think that the program pills only kill flea larva. I have heard that eucalyptus oil will kill the fleas and also leave a scent on the dog that fleas don't like. Has anyone had success with this? If anyone out there has a good suggestion for fleas I am open to them. My dog seems to have the allergies to the fleas and is bitting his backside and tail all up. I have read on the net that it is safe to give dogs benedryl. I have been giving him 1/2 capsul of childrens benedryl for the itching and it helps some, but not totally.Is there anything other than benedryl that works? I am wondering if anyone out there has found the flea solution for a Shi Tzu?