Wood Lock is a medicated oil from Hong Kong that comes in a unique glass bottle.
Since 1968 Woodlock has been created by the China Medicine Laboratory and Wood Lock Medicine Company Limited. Wood Lock was created by Wong To Yick and was based on the formula of the traditional White Flower Oil recipe, which was created by Gan Geok Eng in 1927.
In the United States, it is imported and distributed by Solstice Medicine Company which states all of their products are FDA approved with GMP (Good Manufacturing Practice) accreditation. These guidelines provide minimum requirements that a pharmaceutical or a food product manufacturer must meet to assure that the products are of high quality and do not pose any risk to the consumer or public.
WOODLOCK ACTIVE INGREDIENTS
Also called wintergreen oil, this organic ester is naturally produced by many species of plants, particularly wintergreens. It makes up approximately 50% of Wood Lock, making this product a very strong smelling liniment, to say the least.
Wintergreen oil (along with menthol, eucalyptus oil, camphor, and turpentine oil) is known as a counter-irritant. Counterirritants create a feeling of cold or heat that may overpower the localized sensory information from a sore joint or muscle.
Wintergreen oil is also a salicylate, as evident by its proper name: methyl salicylate. Salicylates are compounds related to aspirin. By using them topically, it may help a patient avoid most of the negative side effects of taking aspirin or aspirin-related compounds by mouth, such as:
ulcers of the stomach and small intestine,
gastritis (inflammation of the stomach)
A study published in 2014 on collagen-induced arthritis in mice concluded, "[methyl salicylate] has great potential to be developed into a novel therapeutic agent for the treatment of rheumatoid arthritis." But, in its pure form, methyl salicylate is toxic, particularly when taken internally. People should never exceed the directions on the label due to the risk of salicylate toxicity (aspirin poisoning). A single teaspoon (5ml) of methyl salicylate contains 7g of salicylate, which is equivalent to more than twenty-three 300 mg aspirin tablets. It has proven fatal to small children in doses as small as 4ml.
Every rose has its thorn, right? To lighten things up (literally), when mixed with sugar and dried, methyl salicylate is triboluminescent. Which is almost as fun to say, as it is to see. It's an optical phenomenon in which light is generated through the breaking of chemical bonds in a material when they are pulled apart, ripped, scratched, crushed, or rubbed. Next time you've got some Wintergreen Life Savers and a dark room, try it out.
For those reasons, Wood Lock was recalled in the United States of America on November 19, 1996 because it lacked child-resistant packaging. U.S. Consumer Product Safety Commission (CPSC) was not aware of anyone who was injured with the product, but recalled it as a preventative measure.
MENTHOL This an organic compound is made synthetically or obtained from mint oils. Approximately 16% of Wood Lock oil is menthol.
Menthol interacts with 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.
Menthol also has weak analgesic (pain-killing) effects due to select activation of the κ-opioid receptor. This receptor is a protein that mediates a variety of effects including changing our perception of pain, consciousness, motor control, and mood.
CAMPHOR This waxy solid has a strong aromatic odor and makes up approximately 10% of Wood Lock. It is found in the wood of the evergreen tree Cinnamomum camphora; Dryobalanops aromatica; Ocotea usambarensis; and dried rosemary leaves (Rosmarinus officinalis). It is easily absorbed through skin and produces a cool-feeling like menthol.
WOODLOCK SIDE EFFECTS
There are no known major side effects for using Woodlock as advised (on the skin, external use only), although one should seek medical attention if a severe allergic reaction occurs. It's also not a good idea to use on broken or damaged skin, and be sure keep it clear of the eyes - ouch.
PRECAUTIONS & WARNINGS:
Methyl Salicylate (wintergreen oil) might cause an allergic reaction in people who are allergic to aspirin or other salicylate compounds, or have asthma or nasal polyps. Use wintergreen with caution if you have one of these conditions.
Wintergreen oil can be poisonous for children. Taking 4-10 mL of wintergreen oil by mouth can be deadly. So keep away from the kiddos and do not use wintergreen oil on the skin of children less than 2 years old.
If you are pregnant or breast-feeding, wintergreen is safe in amounts found in food, but there's inconclusive evidence to know if it's safe in the larger amounts internally or topically. Either clear usage by your doctor, or select a topical gel that does not include wintergreen oil (methyl salicylate) on the ingredients label.
I found an established body of research that may suggest the use of menthol and wintergreen oil 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 off-the-shelf product for pain relief.
Where can you get it? Although you can still find Woodlock (and it's many imitations) via online retailers like Amazon, it's much harder to find it in Chinese markets and health food stores locally due to supply shortages. Information about the company is very limited online, so it does not seem clear whether the company has indeed changed its packaging to comply with the needed child-resistant standards, or has intentions to do so.