ABOUT PO SUM ON
Po Sum On is a Chinese medicated oil that's been the butt of countless massage jokes when referred to as "Pour Some On." Product pages typically site use for the temporary relief of minor aches and pains of muscles and joints due to: sprains, aches, arthritis, strains and bruises.
Po Sum On is Cantonese for what is called in mandarin Bao Xin An or "Protect the Heart's Peace" oil.
According to the Institute for Traditional Medicine, it's produced in Hong Kong by the Po Sum On Medicine Factory and is made by steam distillation of herbs with no synthetic ingredients. In the 100 ml (3.38 oz) bottle, Po Sum on comprises of the following approximations:
57% Peppermint Oil
38% Tea Oil
2% Dragon Blood Resin
1% Cinnamon Oil
>1% Skullcap Root
>1% Licorice Root
PO SUM ON ACTIVE INGREDIENTS
This organic compound can be made synthetically or obtained from mint oils. In Po Sum On's case, the menthol is derived from its top ingredient: peppermint oil.
Menthol stimulates the 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.
In addition, menthol also has weak analgesic (pain-killing) effects that are mediated through a selective activation of the κ-opioid receptor. The κ-opioid receptor is a protein that are responsible for mediating effects such as altering the perception of pain, consciousness, motor control, and mood.
SIDE EFFECTS OF PO SUM ON
There are no known side effects for using Po Sum On topically (on the skin, external use only). Although one should seek medical attention if a severe allergic reaction occurs. Not a good idea to use on broken or damaged skin, and be sure keep it clear of the eyes - ouch.
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.
You may find Po Sum on at a local health store, or on Amazon.