Join Date: May 2011
Location: Northern California
Honestly, if your concern is fleas, Advantage is your best bet. Essential oils don't work as well, you have to re-apply them constantly, and they're not meant to be ingested. Because Advantage travels along the oil layer in the skin, it doesn't cover the entire hair shaft and so if the dogs mouth each other while playing, they won't ingest anything more than a negligable amount. If you use an essential oil spray, you have to really soak them in it down to the skin and it does cover the hair. If you use olive oil as a carrier, it will make the coat oily and dirt will stick to it.
If you have both ticks and fleas, Frontline is your best bet. Advantage won't kill ticks.
About the only thing I use essential oils for is fly/mosquito repellent. Even then, you have to re-apply it 2-3 times a day. Neem and citronella is best for that, along with eucalyptus, clove, cedar, lavender, and citrus oils. I don't know how tea tree and lemongrass would work, but I'm sure they wouldn't hurt. I use a water/alcohol based carrier (about 70% water/30% alcohol). The alcohol evaporates quickly and will stun any bugs hit by it.