My  3 year old lab-mix (apx. 54 lbs) had a severe/life-threatening reaction to Hartz  4in1 topical flea meds last summer, possibly complicated by some dead Girardia  cells that were the only thing found in her blood/stool test.  Her heart slowed  and she was horribly lethargic for months.  It was the first time I had used it  because we were going camping and wanted protection from  fleas and ticks.  She is fine now, but the vet told me to switch to vet-supplied  Frontline as he was convinced it was the Hartz.  I did so and  she began shaking her head within a day (which was her initial reaction to the  Hartz).  I bathed her as fast as I could and gave her Benedryl for a week.  She  never seemed to get sick, but the head shaking continues 3 weeks later.   
We  are going up north on June 5th and I don’t know what  to do.  I have researched essential oils and it seems  that 
Lavendar, Lemon Grass  and  Geranium essential oils between the shoulder blades was most recommended.  My  questions are:
1.      Do they work  for fleas and ticks (lymes disease being my big  concern)
2.      How and how  much should I apply
3.      Will bees be  attracted to the smell, as she is allergic to those  too.
Thank you for any assistance you can  offer.