I just heard a rumor that Lavender oil prevents fleas when used on dogs. Researching this I found one source (Prevetion.com) which provides a claim,
Research has found that lavender can be effective at repelling mosquitos and other arthropods. It’s not clear why the flowering plant can act as a repellent, though—it could just be that the smell doesn’t appeal to bugs, Pereira says. “What is pleasant to you does not have to be pleasant to other humans, other mammals, other vertebrates, or other animals including invertebrates such as mosquitoes,” he says.
They link to the paper, Essential Oils as Repellents against Arthropods.
You can find plenty of other claims some dating back hundreds of years
During the great plagues in Europe, lavender oil was credited as being an insect repellent and used to repel the fleas that were spread by rats.
Is it sound to conclude that lavender oil when sprayed onto a dog will be effective at repelling fleas?