I’m not into killing little critters, so the last thing I would want to do is tell you to use essential oils to kill these guys.  You can, however, use essential oils to “mark out your territory” so to speak.  An example would be to apply a few drops of peppermint essential oil on a damp cloth and wipe it around the entrances in your home you see ants using.  They’ll get the hint and not use that entrance any more. 

You could also add peppermint to your mop water and mop your floors, applying peppermint throughout the hard floor surfaces of your home.  Use peppermint as the main ingredient of your bench spray to keep them out of the kitchen.  You’ll need to do this frequently to keep the results up. 

To protect your dogs from fleas, you could add flea repelling essential oils (as listed) to a natural wash base, then a spray to leave on after you’ve washed your dog.  Consider rubbing essential oils through a clay or herb powder and dusting it through your dog’s coat.  Use your imagination.