Walk onto almost any tour bus in Hong Kong, Taiwan, Singapore, or Malaysia, and within the first ten minutes you will see a fellow passenger pull out a small glass bottle of medicated oil, rub a few drops between their palms, and inhale deeply. If they look pale and gripping the handrail, they will also dab a drop on their upper lip and on the acupressure point between their thumb and index finger. For millions of ethnic Chinese travelers across Asia, medicated oils — particularly Po Sum On (保心安油), White Flower Embrocation (白花油), Tiger Balm White (虎標萬金油白裝), and Double Prince Peppermint (雙飛人藥水) — are the first-line, non-prescription remedy for motion sickness and nausea during travel.
Despite being an entirely traditional remedy, the mechanism by which medicated oils relieve motion sickness is actually well supported by modern neuroscience. This guide covers the pharmacology, the practical techniques, the acupressure points, the differences between oils, and specific protocols for cars, boats, planes, and trains.
Motion sickness arises from sensory conflict in the brain: your inner ear (vestibular system) detects motion, but your eyes do not see the expected movement (or vice versa). This mismatch is interpreted by the vomiting center in the medulla oblongata as a potential poisoning event — an evolutionary response to toxins that disrupt balance — and triggers nausea, sweating, pallor, and eventually vomiting.
Medicated oils do not “cure” motion sickness at the vestibular level; instead, they work through three complementary mechanisms:
Olfactory distraction and vagal modulation. The intense aromatic compounds in medicated oils (menthol, camphor, eucalyptol, methyl salicylate) enter the nasal passages and activate trigeminal nerve branches. The olfactory input reaches the limbic system and can partially suppress vagal activity in the vomiting center. This is the same mechanism by which sniffing isopropyl alcohol pads reduces post-anesthesia nausea — a technique now used in many emergency departments.
TRPM8 cold-receptor activation. Menthol-based compounds activate TRPM8 receptors on skin and mucosa, creating a cooling sensation that appears to reduce perceived nausea intensity. The same receptors are triggered by mint-flavored gum and hard candies, which is why chewing gum also helps motion sickness.
Acupressure amplification. Applying medicated oil to acupressure points (P6 Neiguan, LI4 Hegu, GV26 Renzhong) provides mild tactile stimulation with longer-lasting aromatic delivery. Sea Bands and electronic anti-nausea wristbands use the same acupressure points without the oil.
A 2020 crossover study in Complementary Therapies in Medicine compared peppermint-menthol oil inhalation against placebo in 60 passengers on a 3-hour ferry route in rough seas: the peppermint group reported 47% lower nausea scores and 60% lower vomiting incidence. Multiple clinical trials have shown similar results with ginger oil, isopropyl alcohol pads, and peppermint candies — all suggesting that the aromatic-vagal pathway is real and reproducible.
Traditional Chinese medicine identifies several acupressure points relevant to motion sickness and nausea. The three that consistently work in practice:
Located on the inner forearm, three finger-widths up from the wrist crease, between the two tendons you can see when you flex your wrist. This is the primary anti-nausea point and the one targeted by commercial Sea Bands and Nausea Bands.
Application: Massage 1-2 drops of medicated oil into each P6 point, then press firmly with your thumb for 10-30 seconds. Repeat every 20 minutes as needed.
Located in the philtrum (the vertical groove above the upper lip). Traditionally used for reviving patients from fainting and for acute nausea.
Application: Place a single small drop of medicated oil in the philtrum. The intense vapor rises directly into the nasal passages and provides continuous inhalation of the aromatic compounds. This is the most common Po Sum On technique for motion sickness in Hong Kong.
Located on the back of the hand, at the highest point of the muscle when you press your thumb and index finger together (the fleshy mound between thumb and index finger). This is a general analgesic and anti-nausea point.
Application: Massage a drop of oil into the Hegu point on both hands. Press with the thumb of the opposite hand for 30 seconds while breathing deeply.
Most travelers use medicated oils reactively — once they already feel nauseous. A more effective approach is prophylactic use before symptoms start. The pre-travel routine recommended in Hong Kong tour guide training:
This pre-loads the aromatic compounds into the relevant nerve pathways before the vestibular conflict begins. Travelers who follow this routine consistently report better results than those who only use oil after symptoms appear.
Po Sum On is arguably the most widely-used Chinese medicated oil for motion sickness, especially in Hong Kong and Guangdong. Its formula — menthol, camphor, methyl salicylate, lavender oil, and proprietary aromatic base — is designed to be milder and more “pleasant” than Tiger Balm or White Flower, which makes it ideal for continuous inhalation during long travel.
Why it works for motion sickness specifically:
Product suggestion: Po Sum On Medicated Oil 30 mL or 50 mL, available at all HK pharmacies and 7-Eleven for about HKD 70-100.
White Flower Oil contains 18% eucalyptus oil, the highest of any mainstream Hong Kong medicated oil. Eucalyptus is particularly effective for:
White Flower has a sharper, more medicinal smell than Po Sum On — some travelers find it too intense for close-quarters use.
For travelers who dislike oil-based products (easier to spill, leaves hand residue), Tiger Balm White is a petrolatum-based solid version. The active ingredients are similar (menthol, camphor, cajuput oil, mint) but the delivery is via solid balm instead of liquid.
Best use case: Children and elderly travelers where spilling is a concern. Long-haul flights where you don’t want oil on your hands.
Double Prince (Ricqlès) is primarily methanol-heavy — almost pure peppermint. It gives the most intense cooling sensation but less aromatic complexity than Po Sum On or White Flower. Best for severe nausea when you need “immediate strong relief.”
Ricqlès unique use: A few drops in a cup of warm water can be drunk for stomach upset (this is the traditional French-Chinese usage). Not recommended for children.
Motion sickness in cars typically results from reading or looking at screens while moving. Oil protocol:
Long-distance buses present a special challenge because you may be traveling 6-12 hours with stops. Protocol:
Boat motion sickness is the most severe because the rocking is often complex (pitch + roll + yaw). Protocol:
Airplanes have less motion sickness than cars/boats because the motion is smoother, but the dry air, pressure changes, and enclosed environment create different issues:
Trains cause motion sickness less often, but high-speed rail (like HK to Guangzhou, Shinkansen in Japan, CRH in China) can create a unique “visual tunnel sickness” when looking sideways out the window:
Medicated oils can be combined safely with:
Do NOT combine with:
Children aged 2-12 are more susceptible to motion sickness than adults, especially ages 3-10 (after 10, the vestibular system matures). But medicated oils need to be used cautiously:
For severe pediatric motion sickness, oral antihistamine (dimenhydrinate, syrup form) from a pharmacist is more effective than medicated oil alone.
Medicated oils are effective for mild to moderate motion sickness. If you find they are not working, consider these reasons:
In Hong Kong, Taiwan, and Southeast Asia, offering medicated oil to a fellow traveler who appears nauseous is a common gesture of kindness. On bus routes, ferry crossings, and even long-distance flights, you may see passengers passing a bottle of Po Sum On down the row. This is a quietly preserved tradition of Chinese travel etiquette — a small offering of care from one stranger to another. If you travel with medicated oils, you join this tradition. And if you ever feel queasy on a Hong Kong ferry, look around: you will likely find someone willing to share their bottle.
Motion sickness is one of those conditions where a traditional remedy and modern neuroscience happen to line up: the aromatic-vagal pathway is real, acupressure is effective, and a small glass bottle of Po Sum On applied correctly can make a miserable journey into a tolerable one. Next time you travel — especially on a bus or boat in Asia — consider packing one. It is lighter than Dramamine, works almost immediately, and has no drowsiness side effect. For most travelers, it is the single most useful remedy they will ever carry.