You wouldn't want to use DE topically all the time, b/c it dries out the skin/coat. This is mainly for when you see ticks or fleas on your dog or in the house. The DE comes from fossils and have very sharp spines to the fleas/ticks (not the dogs) which cut their bodies. You'd want to do this outside with good ventilation for the reasons llombaro presented. You can also wear a mask. To keep billowing down, pick up small hand-full carefully, part dogs hair and gently place the DE powder on that area, continuing on whole body, including belly & legs, in small spots.
Dogs and Humans ingest DE! Some people take it religiously!
Neem is a good insect deterrent but there is some controversy about using it around females (human or dogs) if pregnancy is in the future (keeps it from happening) or if already pregnant (possible abortion). But we use it all the time!
Essential Oils (not massage oils) must be mixed with water in a spray bottle or mixed with a "carrier oil". They should not be put straight on to the skin.
Quality Essential Oils should cost $13 or more for 15 ml bottle. If they are cheap, they won't work well.
Best EO repellents: Neem, Rose Geranium, Lemon Grass, Lemon Eucalyptus, Rosemary, Cedar, Tea Tree, Sweet Orange, Eucalyptus, Eucalyptus Blue Gum or Eucalyptus globules, Citronella, Catnip, Yarrow, Pine Needle, Niaouli, Peppermint.
Sprayed on whenever the smell dissapates.
This is a good source: Essential Oils, Pure Therapeutic Grade - Our Complete List
I can pm you the recipes if you'd like.
These products are great too: Natural Flea & Tick Sprays for Dogs, Cats & Home
Per Dr. Pitcairn: “I have not seen problems with garlic in the amounts recommended in the recipes I have used.”
*1/8 tsp to each cup of food OR
*10 to 15 pounds – half a clove
*20 to 40 pounds – 1 clove
*45 to 70 pounds – 2 cloves
*75 to 90 pounds – 2 and a half cloves
*100 pounds and over – 3 cloves
Spring Time Garlic Granulars: Springtime Bug Off Garlic for Dogs | Natural Flea and Tick Repellent for Dogs | Springtime, Inc.