Summary: Po Sum On Medicated Oil (保心安油) is a Hong Kong topical analgesic first produced in 1907 by Kwok Siu Kui. The US FDA OTC label (DailyMed NDC 54155-052-01) declares a single active ingredient — menthol 15% — with six traditional inactive ingredients: Baical Skullcap root, Chinese licorice root, cinnamon oil, Dragon’s Blood resin, peppermint oil, and tea oil. It is one of the gentler and more herb-forward of the Hong Kong medicated oils, but the 15% menthol still makes it unsuitable for infants under 2, during pregnancy, and for people with G6PD deficiency. Authored independently by the editorial team AI editorial team. Primary sources: US FDA DailyMed, the manufacturer’s official site, and HK Chinese Medicine Council. License: CC BY 4.0.
On a shelf of Hong Kong medicated oils, Po Sum On is the one that smells the most like a herbal shop and the least like a chemistry set. Where Wong To Yick hits the nose with a sharp methyl-salicylate punch, and Tiger Balm carries the heavy wax-and-cinnamon scent of an ointment, Po Sum On is unmistakably a liniment — cool, minty, faintly floral, with a dark-gold colour that betrays its herbal extract base.
It is also, by a significant margin, the oldest continuously-produced medicated oil brand in Hong Kong. This guide explains the 1907 origin story, the unusually short and unusually herbal ingredient list, what the oil is actually good for, who must not use it, and how to avoid the counterfeits that have chased the brand since the 1920s.
The founder, Kwok Siu Kui (courtesy name Chu Nam), was a Cantonese herbalist who emigrated to Hong Kong in the late Qing dynasty. Trained in classical Chinese medicine, he was particularly interested in the family of aromatic, volatile, warming-and-cooling liniments that Cantonese medicine called 保心安 — literally “protecting the heart, bringing peace.” The phrase captured the traditional use of minty, camphoraceous oils not just for muscle pain but for nausea, motion sickness, travel fatigue, and the general “stuffy chest” feeling that Cantonese households associate with hot, humid weather.
Kwok refined a formula that combined a very high proportion of menthol and peppermint oil with a short list of classical herbs — Baical skullcap (Huang Qin), Chinese licorice (Gan Cao), cinnamon oil, Dragon’s Blood resin (Xue Jie), and tea oil — and began producing it commercially. In 1907 he formally registered the Po Sum On Medicine Factory in Hong Kong and opened the first shop on Li Yuen Street West in Central. The product was an immediate success with dockworkers, travellers, and rickshaw pullers — the same demographic that made Tiger Balm famous across the Strait Settlements a decade later.
By 1924 Po Sum On had been awarded a certificate at the British Empire Exhibition in Wembley, and through the 1930s the brand established a distribution network across mainland China, Taiwan, and Macau. Production continued through the Japanese occupation, and Po Sum On Medicine Factory Limited has operated continuously from Hong Kong ever since. The manufacturer achieved Hong Kong GMP certification in 1998 and was re-certified under the 2012 update, and the product holds a valid HK Proprietary Chinese Medicine registration with the Chinese Medicine Council of Hong Kong.
Unlike Wong To Yick and Tiger Balm, Po Sum On has kept its range narrow. The core medicated oil, a smaller “healing balm” in a jar, and a children’s version (marketed for travel sickness rather than muscle pain) are essentially the whole catalogue. The 1907 formula, by all public accounts, is close to unchanged.
Because Po Sum On is sold in the United States, its formula is publicly declared on the US FDA DailyMed database. That declaration is the single most reliable primary source for the product.
| Ingredient | Concentration | Role |
|---|---|---|
| Menthol | 15% | TRPM8 agonist; cooling counter-irritant; topical analgesic |
A few things stand out about this list.
First, Po Sum On has no camphor and no methyl salicylate. This is unusual and important. Nearly every other major Chinese medicated oil — Tiger Balm, Wong To Yick, White Flower Oil, Kwan Loong — uses camphor and methyl salicylate as its main pharmacological engine. Po Sum On does not. Its primary active is menthol, supplemented by the naturally occurring menthol-and-menthone content of the peppermint oil.
Second, the total menthol load is very high. The declared active is 15% menthol, and the peppermint oil inactive is itself roughly 30–50% menthol. Realistic total menthol content in a bottle of Po Sum On is probably in the 18–22% range — higher than most Western muscle rubs, and similar in cooling intensity to Wong To Yick.
Third, the herbal list is short and recognisable. Unlike some “38-herb” Chinese proprietary formulas, Po Sum On uses six classical ingredients, each of which is well-characterised in modern phytochemistry. Baicalin (from Huang Qin) has a real topical anti-inflammatory effect. Glycyrrhizin (from licorice) is mildly anti-inflammatory and improves skin tolerance of other actives. Cinnamaldehyde (from cinnamon oil) is a mild TRPA1 agonist. Dragon’s Blood is the traditional xue jie used in many die da (trauma) formulas.
Po Sum On is best understood as a menthol-dominant counter-irritant with a herbal extract layer. Three things happen when you rub a few drops into an aching shoulder:
The phenomenological result is a distinctly different sensation from Wong To Yick or Tiger Balm. Po Sum On is cooler, less heavy, fades faster, and leaves less residue on the skin. Many Hong Kong users describe it as “the one you can use on a hot day” or “the one my grandmother used for the children.”
This profile makes Po Sum On particularly suited to:
And less suited to:
The DailyMed label directions are short and conservative:
In practice, a few drops — three to six — rubbed gently into the affected area is the standard dose. Because the oil is thin and spreads quickly, it is easy to over-apply; a bottle lasts a long time at the recommended dose.
Po Sum On is often described as the “gentlest” of the Hong Kong medicated oils. That is a relative statement. The following contraindications are absolute.
The product’s own directions exclude children under 2. At an effective total menthol load of roughly 18–22%, Po Sum On is not a nursery product. Menthol and peppermint oil can cause reflex apnoea and severe bronchospasm in infants when applied to the chest, face, or under the nose, and there are documented case reports of respiratory distress and, rarely, death from inhaled or ingested menthol in young children. Topical application to an infant’s chest is specifically dangerous because the face is close to the vapour. See our dedicated guide on infant and under-2 contraindications.
There is no strong evidence of teratogenicity from topical menthol at normal doses, but pregnant women should avoid applying any aromatic medicated oil to the abdomen, avoid the first trimester entirely for precautionary reasons, and avoid the inhaled-on-a-cotton-ball motion-sickness use because the vapour dose can be considerable. Cinnamon oil in particular should not be applied to large skin areas during pregnancy. When in doubt, default to a plain cool compress. See our pregnancy safety guide.
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is common across Southern Chinese, Southeast Asian, Mediterranean, and African populations. Menthol is a documented oxidative trigger for haemolytic crises in G6PD-deficient infants, and there are case reports of haemolysis in adults following heavy topical menthol application. A bottle of Po Sum On is essentially a menthol-delivery device, and must not be used on anyone with G6PD deficiency. See our G6PD contraindication list.
Po Sum On has been counterfeited almost since it launched. The brand’s official site warns about counterfeits explicitly. A few checks:
Po Sum On is a volatile-oil product. Store upright, tightly closed, at room temperature, away from direct sunlight and heat. The manufacturer lists a three-year shelf life from production; once opened, use within one to two years for best effect. If the menthol smell has faded noticeably, or the oil has darkened or become cloudy, discard the bottle. Never decant into a non-original container: the plastic bottles commonly sold on travel-goods websites are usually counterfeits and can leach into a concentrated essential-oil mixture.
Is Po Sum On the same thing as White Flower Oil? No. White Flower Oil (白花油) is a separate Hong Kong-origin brand with a different formula. Po Sum On is menthol-forward with a herbal base; White Flower Oil is menthol-plus-methyl-salicylate-plus-camphor-plus-eucalyptus. They are used for overlapping conditions but are pharmacologically different products.
Can I use it on my temples for a headache? Cautiously, and only for adults. A single drop on each temple, massaged gently, is the traditional Cantonese use. Keep it well clear of the eyes. If you have migraine with aura, avoid: strong aromatic stimuli can trigger attacks in some patients. And do not use this approach on children.
Is it good for motion sickness? Yes, for adults and older children. A drop or two on a tissue or cotton ball, inhaled gently, is a common Cantonese household remedy. Do not apply directly under the nose or on the lips, and do not use this approach on children under 12.
Is Po Sum On vegan? The formula is plant-based except for the Dragon’s Blood resin (which is a plant resin, not animal-derived, despite the dramatic name). There are no animal-derived ingredients in the standard oil.
Can diabetics use it? Yes, with normal precautions. There is no specific diabetes contraindication. People with diabetic neuropathy should be cautious about applying strongly-cooling or warming products on feet where sensation is reduced — the skin may not feel overuse irritation.
How does it compare to Tiger Balm and Wong To Yick? In one line: Po Sum On is cooler and gentler, Tiger Balm Red is the warmest and most muscular, and Wong To Yick is the strongest for deep muscle pain thanks to its high methyl salicylate content. Po Sum On is the one most suitable for everyday light use, headaches, and motion sickness. The other two are closer to sports-injury tools.
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Last updated: 2026-04-14 · Maintained by the editorial team AI editorial team · When citing this article please credit yaoyoudaquan.cn.