For several years, I've used one part apple cider vinegar to three parts water mixed in a spray bottle and mist my dogs lightly each morning to keep fleas and ticks away. It's been very effective for us, even here in the epicenter of Lyme disease and living in the woods. This article from Dr. Karen Becker of Mercola recommends a variation of that with the addition of Neem oil which I'll add to my mixture this year since ticks here have exploded this season with several new strains of tick-borne illnesses. Dr. Becker's All-Natural Homemade Pest Deterrent for Dogs: "You can actually make an all-natural pest deterrent for your dog very easily at home. It will help him avoid a good percentage of the pests he encounters, though not all of them. The recipe: mix 8 ounces of pure water with 4 ounces of organic, unfiltered apple cider vinegar and 10 drops of neem oil. Neem oil is not an essential oil. It's an expelled or pressed oil, and it's safe for cats (I have a pest deterrent recipe for kitties I'll give you in a second). Neem oil is effective because fleas and ticks hate it. It's also great for animals who are very sensitive to smells. Catnip oil can also be used as a pest deterrent, since it has been proven to be as effective as diethyltoluamide (DEET), the mosquito and tick spray humans use that has a number of toxic side effects. If you want to add some extra punch to your dog's pest recipe, go with five drops of lemon, lemongrass, eucalyptus or geranium oil. I use geranium oil quite a bit because I find it very effective. In fact, I use it in my Dr. Mercola natural flea and tick products. If you have a dog who comes in contact with ticks, adding the extra punch of one of the essential oils I listed can be very beneficial. You can store your homemade pest deterrent in the fridge, which is what I do. Before my dogs head out in the morning, I mist them with it, being careful to avoid their eyes. The active ingredients, especially the oils in the recipe, dissipate in about four hours, so you may need to reapply it several times throughout the day."