The venerable NY Times launched an investigative report into the claims and data associated with all-natural insect repellents.
Their conclusion was very clear deet, picaridin and permethrin are the most effective repellents. The article is also quite educational and informative.
Here’s the link: Why Essential Oils Make Terrible Insect Repellents
NPR also did an article and feature story in 2015. This article has been updated