Peppermint oil is extracted from the leaves of the peppermint plant, which is actually a hybrid mint - a cross between watermint and spearmint.
It is originally native to Europe and the Middle East, but now cultivated and grown all over the world and almost all climates.
Sometimes peppermint is found growing in the wild alongside its parent plants, but being a hybrid, it is typically sterile and produces no seeds. Peppermint spreads in vegetation quickly through its root system.
At this time, there is limited research specifically on peppermint oil's topical applications. Much research is focused on its possible relieving effects of irritable bowl syndrome.
However, there is an established body of research on menthol, which is found in high concentrations in peppermint oil.
Menthol enhances cooling sensations via stimulating the cold-sensitive transient receptor potential channel melastatin 8 (TRPM8). This receptor is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin.
It also has weak analgesic (pain-killing) effects due to its selective activation of our κ-opioid receptor. This protein mediates many effects including changing our perception of pain, consciousness, motor control, and mood.
I found an established body of research that may suggest the use of peppermint oil (menthol) for mild pain relief. Given the very low risk and very limited side effects, it would seem worth a try for individuals seeking a complementary and/or natural product for pain relief.