There are so many flee and tick preventions on the market, it can be hard to chose. I always try to approach health in a holistic way for both myself and Finn. So, we make a holistic mix of different ingredients you can find at a Grocery Store. We go to Whole Foods because I know they have all of the ingredients and its close to our apartment in NYC. That being said, while a holistic approach works for us, it may not work for everybody so please consult your vet before giving the below recipe for your dog. Try making the below recipe and sprinkling it on your dogs food in the morning and evening. 
-1 teaspoon for small dogs, 1 tablespoon for medium dogs, 2 tablespoons for larger dogs
Qty Measure Ingredient
2 cups​ ​nutrional yeast
1 Cup lecithin granules
1/4 Cup alfalfa powder (or kelp powder)
3 tsp sea calcium(or 5 tsp calcium egg shells-ground in food processor)
1 tsp garlic powder
1/4 tsp vitamin c
add fresh garlic and fresh parsley to each meal
Instructions: Mix up and keep in the refrigerator