Here is a list I found when I started to research essential oils.http://en.wikibooks.org/wiki/Beekeeping/Guide_to_Essential_Oils
Make sure you are using the real stuff and not that aroma crap
Also here is a recipe that is similar to Honey-B-Healthy.http://www.gardenfork.tv/essential-oil-recipe-for-honeybees
Here is the Honey-B-Healthy Flyer with their promotions and ingredients. http://www.bee-commerce.com/content/freedownloads/HoneyBHealthyInfo.pdf
Use at your own risk; It has been known to occasionally cause robbing behavior due to its great appeal to bees.
You can also use this natural formula instead of smoke for your bees, it has been said to calm them.
I have not sprayed my bees yet but will use it soon.
Read the links above
Essential oils are passed from feeding bees to other bees and larvae through trophallaxis. Essential oils thereby pass to the brood and poison any female Varroa that attempt to parasitically feed on the larva. Just one of the benefits I learned about. Also just to add I will be only feeding this to my bees once every 2-3 months and not during honey harvest.