Be careful which peppermint oil you use, use ONLY food grade... Just a drop or 2 on your dogs paws (all 4 pads)
I have been doing some reading and from what I have read peppermint oil (the essential oil) should not be used on paws because they will lick it and it shouldn't be ingested..
Remember if you cannot cook with the peppermint oil then you cannot use it on your dog's paws.
I know peppermint oil works awesome for many other things and in humans as well. My friend buys peppermint leafs and makes a tea before bed and it helps her insomnia..
Anyhow here are some links.
HowStuffWorks "Peppermint: Herbal Remedies" How to Calm Dogs with Peppermint Remedy | eHow.com How to Calm Dogs With Peppermint Oil on Paws | DailyPuppy.com