Vectra topical repellent/insecticide

I use Essential oils for flea ,tick and Mosquitos. Geranium oil for ticks, eucalyptus for Mosquitos, lemongrass fleas, lavender oil, etc. I mix them together with water. Also every few days, put a drop on their collars. Sentry makes a good essential oil spray. It's called Natural Defense flea and tick spray. I've used this for two years with good luck. I always do tick checks, comb with flea comb, and if ever a flea infestation, I carry Food grade DE dirt. Never had to use it yet. I don't use heartworm preventative either. Takes a lot for variables than just the advertise "one bite is all it takes to get heartworm". I do heartworm test in early summer and again late fall or early winter. I don't leave them out when Mosquitos are active. I was a user of Frontline, until that one application caused my dog to have a grand maul seizure at 15 yrs old. And then several more until he succumbed to them at the age of 15 1/2, No more chemicals, pesticides, insecticides will ever touch my dogs or cat again. Must be the reason cancer is the number 1 killer of dogs. I don't use fertilizer or chemicals on my yard either. Just my two cents.