Thailand’s markets come alive with the fragrance of som-o, or pomelo, especially during the cool season when its hefty, grapefruit-like fruits are stacked high. Many Thais relish its sweet-tart segments at temple fairs or New Year merit offerings. Yet, the greatness of the pomelo (Citrus grandis (L.) Osbeck)—known locally by names such as โกรัยตะลอง, มะขุน, มะโอ, ลีมาบาลี, and สังอู—extends far beyond the fruit bowl. For centuries, Thai traditional medicine has harnessed the thick, aromatic peel of som-o for remedies thought to ease coughs, swelling, skin woes, and indigestion. But how much of the old wisdom has stood up to scientific inquiry? Today, with both respect for heritage and a critical eye, we explore what research reveals about pomelo peel’s healing promise—and where prudent caution remains essential.
Pomelo’s place in Thai herbalism is rooted in everyday rituals and household encounters. The vibrant zest often perfumes old-style Thai soaps and balms, while slices of dried peel simmer in teas, handed down as grandmother’s answer to stubborn phlegm or bloating after a festive meal. In folklore, pomelo peel is mentioned as a natural anti-itch for insect bites or as a poultice for minor swelling. Such uses are woven through local knowledge, temple teachings, and community-based medicine, reflecting a balance of faith, trial, and error that underpins Thai herbal tradition (Wikipedia; Yantra Herbs).
Behind these deeply Thai practices lies a global plant of complexity and scientific fascination. The pomelo is the largest citrus species, believed to be an ancestor of grapefruit, and is native to Southeast Asia (Wikipedia). Traditional uses go beyond Thailand: in China, its dried peel—called ‘chen pi’—is used for digestive complaints, while in Vietnam, the essential oil features in folk balms and rituals for luck. Modern pharmacological research has now begun to shine a spotlight on these old remedies, especially on the thick, spongy exocarp—the outermost layer of the fruit.
Scientific studies reveal that pomelo peel is rich in bioactive compounds, including flavonoids (notably naringin, naringenin, and hesperidin), vitamins, coumarins, carotenoids, polyphenols, essential oils (predominantly limonene), and natural polysaccharides (PMC8527587). These phytochemicals are not only responsible for the fruit’s refreshing aroma but may account for its traditional healing properties. Comprehensive reviews confirm that the peel contains a diverse range of antioxidants, anti-inflammatory, antimicrobial, anticancer, and metabolic-regulating agents (PMID: 34657477).
Much excitement among researchers centers on the peel’s antioxidant potential. Flavonoids and polyphenols, abundant in the peel, neutralize harmful free radicals—molecules implicated in aging, cancer, and cardiovascular diseases. Laboratory assays comparing different parts of pomelo consistently show its peel and juice to have higher antioxidant activity than many other citrus fruits (Makynen et al., 2013, Chang & Azrina, 2017). Thai studies in particular highlight that local cultivars such as ‘Thong Dee’ and ‘Kao Nampueng’ have above-average levels of beneficial compounds.
Traditionally, in Thai households, a decoction (boiling process) of the peel is sometimes employed for coughs or phlegm. Modern science lends support: in both Thai and international lab investigations, extracts of pomelo peel exhibit antimicrobial effects against pathogens commonly involved in respiratory and gastrointestinal complaints (ResearchGate; SPMC Journal). For instance, a clinical trial in the Philippines compared a 12.5% pomelo peel ointment with standard mupirocin ointment in treating localized impetigo contagiosa (a bacterial skin infection). Results showed the pomelo peel ointment to be similarly effective and well-tolerated, hinting at a future where herbal remedies could supplement or reduce reliance on antibiotics—particularly valuable in regions like rural Thailand, where access to pharmaceuticals may be limited.
The anti-inflammatory and anti-swelling uses persist in Thai folk medicine, and here too, laboratory evidence mounts. Animal studies and cell culture experiments reveal that pomelo peel extracts, especially those containing polysaccharides and coumarins like auraptene, can significantly diminish inflammatory markers and reduce swelling, both internally and externally (PMC8527587). Although these effects require confirmation in large-scale human studies, their alignment with traditional uses is striking.
Another common use in Thailand—soothing indigestion—is partially explained by scientific research. Flavonoids and bitter coumarins in the peel stimulate digestive secretions and can modulate gut motility, as shown in both animal and in vitro studies. Such effects parallel traditional decoctions administered for bloating and colic.
Beyond these core uses, pomelo peel’s chemistry opens new doors: studies have found that its essential oils can suppress fungal and microbial growth, inhibit the formation of harmful compounds in food, and even aid as natural preservatives (ScienceDirect). Innovative environmental applications—such as oil spill clean-up or bio-based packaging—also surface, echoing the age-old Thai ethos of using every part of the plant.
Pomelo peel’s anticancer potential, too, is beginning to draw attention. Laboratory research finds that certain limonoids, especially from the seeds and peel, can trigger the self-destruction of tumorous cells (a process called apoptosis) and inhibit the formation of new blood vessels that feed tumors (PMC8527587). While far from a cancer cure, these findings support its place as a functional food within a balanced Thai diet. In addition, extracts have shown the ability to regulate blood sugars and lipids in animal models, likely due to the presence of specific flavonoids and polysaccharides. This points to a scientifically validated future for pomelo peel in managing metabolic syndrome—a health challenge increasingly noted in modern Thai society.
Practical application is nonetheless marked by both promise and prudent restraint. Pomelo peel is non-toxic when used in traditional culinary or folk medicine amounts, but laboratory concentration effects do not always translate into safe or effective home use. The peel is highly bitter, and excessive ingestion may aggravate sensitive stomachs or interact with certain medicines. Most notably, like grapefruit, pomelo can interfere with some prescription drugs (such as statins or blood pressure medications), potentially increasing their concentration in the body (Wikipedia). Thai healthcare professionals urge caution: individuals managing chronic diseases or on regular medication should always consult a medical provider before experimenting with concentrated pomelo remedies.
From a cultural perspective, pomelo’s role in Thai life transcends its pharmacology. The fruit is an auspicious symbol, linked to good fortune and merit-making. At temple fairs, the challenging process of peeling som-o—a family activity in itself—reflects the patience and community spirit at the heart of Thai society. The folk wisdom around its uses reminds us that traditional healing is as much about care and context as about bioactive molecules.
In conclusion, the story of pomelo peel is an inspiring example of old and new knowledge meeting in the middle. Many long-cherished uses—soothing coughs, easing swelling, freshening up, or aiding digestion—find real support in laboratory and limited clinical trials. The rich palette of phytochemicals offers genuine health-promoting potential, especially in the context of a diverse, plant-rich Thai diet. Yet, science rightly presses for further study, particularly around safety at medicinal doses, interactions with pharmaceuticals, and efficacy in wider populations.
For Thai readers interested in exploring pomelo peel’s benefits, a few practical steps are suggested: Consider including moderate amounts of zest or dried peel in cooking or as part of a traditional herbal tea. For skin or household uses, ensure proper hygiene and avoid applying raw peel to open wounds. Always seek guidance from a qualified traditional Thai medicine practitioner or a healthcare provider—especially if you have underlying conditions or take prescription medication. Remember: the wisdom of the ancestors was built on caution as much as creativity.
Ultimately, pomelo stands as a testament to the intricate tapestry of Thai traditional medicine, entwining culture, cuisine, and community care. As research continues, this “giant of citrus” may yet yield new secrets that inspire the next generation of remedies, both in Thailand and beyond.