Wood Lock Oil is a topical analgesic used to treat mild to moderate muscle pains and aches. It is widely used in China, its country of origin, and is sold in many other countries. Considered an herbal remedy, this product is a mixture of essential oils, including menthol, which can be easily discerned by Wood Lock Oil's pungent aroma. It also contains methyl salicylate and cinnamon extract, as well as other proprietary herbal ingredients. It commonly is used to treat sore muscles and joints, to relieve back pain and to ease arthritis.

Wood Lock Oil can be applied topically in many ways. The traditional method in China is to use a method consisting of locating the origin of the pain and applying Wood Lock Oil. The spot is then subjected to pressure, usually by hand, for at least fifteen minutes. This method is said to combine the effects of the Wood Lock Oil while promoting a proper balance of chi within the body. As with many herbal remedies, the oil and its application methods have been held under close scrutiny by the science-based medical community. Wood Lock Oil is known to consist of 50% methyl salicylate. This ingredient has been the subject of recalls and has been blamed for deaths. Methyl salicylate is closely related to the main ingredient in aspirin, acetylsalicylic acid.

In the United States (U.S.), a popular form of this oil was once recalled due to “improper packaging.” The bottle, following the requirements for natural oils, involved a typical cap with no child protection devices — young children could encounter the bottles and ingest dangerous amounts of the oil. The ingredient called methyl salicylate, or oil of wintergreen, is known to cause an allergic reaction in children that could result in serious injury or death. This recall was not due to any reported injuries, but rather a pro-active step to protect toddlers.

Athletes have also suffered from injury or death after applying large amounts of methyl salicylate to vast portions of their bodies. Injury or death is often caused by absorbing large amounts of methyl salicylate through the skin. One of the most prominent of these cases was the death of a U.S. college athlete in 2007. The product is considered safe, however, when the oil is used in accordance with its packaging instructions and while exercising due caution.

The popularity of Wood Lock Oil has increased with the interest in herbal remedies and homeopathic medicine. It offers a way of treating muscle aches and general pain without ingesting medication. Commercially available Wood Lock Oil is manufactured in Hong Kong and distributed through dealers in many countries.