Cong Bai
StarAllium fistulosum L.
Traditionally used for
- Colds & fever
- Digestion
- Urinary & fluids
- Skin
Cautions & contraindications
- Bleeding disorders
☯ TCM Properties
Induces Sweating and Releases the Exterior; Disperses Cold; Warms and Unblocks Yang; Reduces Swelling and Resolves Toxicity; Promotes Urination
Traditional Chinese Uses
Cong Bai (scallion bulb, welsh onion bulb) is a warm, acrid herb used primarily to gently disperse Wind-Cold from the Exterior and promote mild sweating at the early stages of a cold or flu with chills. Its warming nature also dispels internal cold to relieve abdominal coldness and pain. Applied externally as a poultice, it reduces swellings and draws out toxins from abscesses and sores. Its accessibility as a kitchen ingredient makes it a readily available home remedy.
Western Herbalism Properties
Relationships
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Botanical Description
Allium fistulosum is a clump-forming herbaceous perennial in the Amaryllidaceae (subfamily Allioideae), believed to have originated in northwestern China and now cultivated worldwide, particularly across East Asia, as the Welsh, Japanese bunching or spring onion. Plants grow 30-60 cm tall and lack a true bulbous base, instead forming an elongated, slightly swollen white pseudostem that grades into hollow, cylindrical, blue-green leaves 1-2 cm in diameter. Several leaves arise from each shoot and the whole plant has the characteristic pungent onion aroma. In the second year, hollow flowering scapes emerge bearing a single terminal, spherical umbel 3-7 cm across, packed with many small, six-tepalled, greenish-white flowers with conspicuously protruding stamens. Pollination is by insects and the fruit is a small capsule containing black, angular seeds. The species thrives in fertile, well-drained soils in full sun and is propagated by seed or division of offsets.
Active Constituents
Isoalliin (S-1-propenyl-L-cysteine sulfoxide)
S-alk(en)yl cysteine sulfoxide (non-protein sulfur amino acid)Concentration: not reliably quantified in the dried drug; pyruvate release, the usual proxy for total cysteine sulfoxides, is generally higher in Allium fistulosum than in A. cepa, and higher in the bulb than in the leaf
The dominant cysteine sulfoxide of Welsh onion and the storage form of its pungency. On cell damage alliinase cleaves it to 1-propenyl thiosulfinates, ammonia and pyruvate, which is what makes crushed Cong Bai acrid and antimicrobial. Its biosynthesis in this species was traced in 2025 through S-1-propenyl-L-cysteine, generated by the gamma-glutamyl transpeptidase AfGGT1.
Thiosulfinates (including material reported as allicin)
Organosulfur compound (alkyl alkanethiosulfinate)Concentration: measurable in the fresh stalk; blanching at 100 degrees C removes roughly 73% of it, so decocted material carries far less than fresh
These are the short-lived breakdown products of the cysteine sulfoxides and carry most of the antibacterial and antifungal activity attributed to fresh Allium. They are thermolabile and volatile, which is the pharmacological reason classical texts add Cong Bai at the very end of a decoction rather than boiling it with the rest of the formula.
Quercetin and its glucosides
Flavonol and flavonol glycosidesThe main flavonoids of the green leaf and outer scales, and the compounds most often invoked in the antioxidant and antibacterial in vitro work on this species. Welsh onion is a considerably poorer quercetin source than the bulb onion Allium cepa, so activity data generated on A. cepa should not be transferred to Cong Bai.
Fructans and other dietary fibre polysaccharides
Fructo-oligosaccharide and non-starch polysaccharideThe bulk carbohydrate of the stalk, with a complex monosaccharide composition and glycosidic linkage pattern. These are fermentable fibres rather than a pharmacologically active fraction, and they are the reason Allium foods are restricted on low-FODMAP diets.
⚠ Drug Interactions
Warfarin and other vitamin K antagonists
Cong Bai as an official drug is the white bulb and lower stalk, which contributes little vitamin K1. The green leaf is a green leafy vegetable and carries phylloquinone as such vegetables do. No interaction study exists for Allium fistulosum specifically; the concern is generic to leafy greens and to inconsistent, not high, intake.
Clinical note: Only relevant if a patient eats large and variable amounts of the green tops. Advise steady intake rather than avoidance, and do not extrapolate garlic anticoagulation data to this species.
Antiplatelet and anticoagulant drugs (aspirin, clopidogrel, DOACs)
Allium organosulfur compounds inhibit platelet aggregation in vitro, but essentially all of that evidence comes from Allium sativum and its ajoene and allyl thiosulfinates, not from Allium fistulosum, whose sulfur profile is dominated by 1-propenyl rather than allyl species. No bleeding events attributable to Welsh onion have been reported.
Clinical note: No restriction is warranted at culinary or standard decoction doses. Flagged only so that garlic-derived warnings are not applied to this herb by default.
Honey (classical dietary proscription)
Chinese dietetic tradition proscribes taking Cong Bai together with honey. There is no pharmacological mechanism, no case report and no analytical work supporting a real incompatibility. It is recorded here because practitioners are taught it and patients ask about it, not because it is an evidenced interaction.
Clinical note: Treat as a traditional convention, not a safety restriction. Do not present it to a patient as a pharmacological hazard.
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Both gently release the exterior; together they induce a mild sweat for the very early stage of a wind-cold invasion without harsh diaphoresis.
Core pair of a classical formula — Cong Chi Tang, Zhou Hou Bei Ji Fang (Ge Hong)
Evidence Tier
Moderate evidence · 2 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
1
1 verified · 0 unverified
Other clinical trial
0
Observational / case report
0
In vitro / animal
1
1 verified · 0 unverified
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Effects of Allium fistulosum L. (Green Onion) Root and Avena sativa L. (Oat) Mixtures (WCO31) on the Height of Children: A Multi-Center, Randomized, Double-Blind, Placebo-Controlled Clinical Trial
150 Korean children aged 6 to 8 took 1.2 g/day of WCO31, a mixture of Allium fistulosum root and oat, or placebo for 24 weeks. Height, growth rate and height-for-age Z-score were all significantly better in the treated group, with no safety signal. This is the only randomised human trial in this species that we could verify, and it tests a two-component root-and-oat extract for a growth endpoint, not Cong Bai as an exterior-releasing herb; it says nothing about the traditional indication.
Functional Foods in Gastrointestinal Health: The Role of Moringa, Artichoke, and Welsh Onion in Managing Diarrhea
In castor-oil-induced diarrhoea in Wistar rats, Allium fistulosum preparations reduced stool frequency, improved stool consistency and modulated intestinal motility alongside antioxidant and anti-inflammatory changes and better epithelial integrity. The authors attribute the Welsh onion effect largely to its fatty acid and fibre profile. Rodent data only, and the plant material was Tunisian organic-farm produce rather than a Chinese pharmacopoeial drug.
Historical Texts
Shen Nong Ben Cao Jing
Han dynastyMing Yi Bie Lu
Southern and Northern DynastiesShang Han Lun
Han dynastyBen Cao Gang Mu
Ming dynastyReferences
- Kim SH; Yoon J; Han J; Seo Y; Kang BH; Lee J; Ochar K. Green Onion (Allium fistulosum): An Aromatic Vegetable Crop Esteemed for Food, Nutritional and Therapeutic Significance . Foods (2023) [DOI]
- Zhu M; Xu H; Deng Z; Hou M; Liu L; Wang Y. Identification of S-1-propenyl-L-cysteine as the catalytic product of AfGGT1 and a key intermediate in isoalliin biosynthesis in Allium fistulosum. L . Food Chemistry: Molecular Sciences (2025) [DOI]
- Li Y; Ma J; Cao Y; Yang D. Efficient removal of allicin from the stalk of Allium fistulosum for dietary fiber production . npj Science of Food (2024) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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