What Is This 'Watermelon Medicine' And Why Chinese People Use It For Ulcers & Sore Throats
Also known as Xi Gua Shuang.
By Jeremy Ng — 28 May 2025, 12:20 PM
If you grew up in a Chinese family, you've probably seen this iconic bottle with a green cap at home
Xi Gua Shuang, or watermelon trost, is a time-honoured traditional Chinese remedy used to treat mouth ulcers, sore throats, and toothaches.
In Malaysia, it's commonly available in a fine dark-green powder packaged with a nozzle-style spray tube, designed to help target hard-to-reach areas in the mouth. Anyone who's tried it knows the sensation well, a bitter, minty sting that sometimes catches you off-guard, especially if you accidentally over-spray and end up coughing.
Despite that, many users continue to swear by its effectiveness.
Known for its anti-inflammatory, antibacterial, and analgesic properties, Xi Gua Shuang not only numbs pain but also accelerates healing. Most people report feeling relief within minutes, with visible improvement often by the next day.
But what you may not know is that one of the main ingredients in this traditional remedy is... Watermelon rind!
Watermelon peel extract is one of the main ingredients, and is derived from the rind of the watermelon (the white part beneath the green skin), which is said to "reduce heatiness" and relieve pain in traditional Chinese medicine.
Other ingredients include menthol and Chinese herbs like Rhizoma Belamcandae and Bulbus Fritillariae Cirrhosae (Chuan-Bei-Mu).
Interestingly, Xi Gua Shuang dates back to the Qing Dynasty, and has been around for approximately 250 years
Its earliest documentation appears in the "Yang Yi Da Quan" ("Great Compendium of The Medicine of Sores"), authored by Gu Shicheng during the Qing Dynasty. Gu Shicheng was active around 1773, and his work compiled extensive knowledge on ulcer treatments of that era.
Here's the traditional method of making Xi Gua Shuang:
- A ripe watermelon is chosen, and a cavity is carved into its flesh
- The cavity is filled with mirabilite (Glauber's salt)
- The watermelon is resealed and stored in a cool, ventilated place
- Over several days, a crystalline frost forms on the exterior of the watermelon rind
- This 'watermelon frost' is carefully scraped off and collected for medicinal use
Today, the remedy has been adapted to modern versions, combining traditional ingredients with convenience
In fact, Xi Gua Shuang is readily available over the counter at pharmacies and online stores. So, the next time you have an ulcer, you know what to do.
