Educational information, not medical advice — ask your doctor or midwife.
Ya Zhi Cao is the dried above-ground part of the Asiatic dayflower (Commelina communis), a common blue-flowered weed. It is used in Chinese herbal medicine as a single herb to cool fevers, ease a hot sore throat, and help the body pass more urine.
Practitioners use it for short, sharp problems rather than long-term ones. Typical uses are a feverish cold, a red painful throat, or puffiness and difficult urination. Fresh crushed leaves have also been laid on boils, insect bites and snake bites in folk practice.
Here is the honest verdict. Ya Zhi Cao has a recognised place in classical Chinese formularies, but published human trials are essentially absent, so we cannot say what it does in people. Traditional use tells you a plant has been trusted for a long time; it is not proof that it works, and that applies to everything described on this page.
In Chinese medicine terms, Ya Zhi Cao is described as cold and sweet-bland. It is said to clear heat, resolve toxin, and drain water downward through urination. Those are traditional descriptions of what the herb does, not measurements of what happens in the body.
Laboratory and animal studies suggest a few possible actions. Extracts have increased urine output in animals, reduced markers of inflammation (swelling and irritation) in test systems, and slowed the digestion of starch in the gut.
None of this has been confirmed in people. Treat any mechanism you read about Ya Zhi Cao, including the ones above, as an unproven idea rather than a settled fact.
Ya Zhi Cao is nearly always used as a water decoction, meaning the dried herb is simmered in water and the liquid is drunk. This is the form Chinese herbalists use most.
You may also meet it as loose dried herb sold by weight, as granules or powder made from a concentrated water extract, or as fresh herb.
Fresh crushed herb is applied to the skin in folk practice for bites and boils. It is occasionally one ingredient in a multi-herb formula rather than a stand-alone remedy. Standardised capsules and tinctures are uncommon in Western shops.
Ya Zhi Cao appears in Chinese materia medica writings from around the Tang dynasty onward and is listed in modern Chinese pharmacopoeial texts as a heat-clearing, toxin-resolving herb. The plant is also eaten as a wild green and used in folk remedies in Japan and Korea. Its standing is solid within Chinese practice but it is a secondary, everyday herb rather than a famous one.
Get medical help straight away if you have a snake bite, a fever above 39C (102F), a stiff neck, trouble breathing or trouble swallowing, or if you cannot pass urine at all.
See a doctor within a day or two if your fever, sore throat or burning urination has not improved after three days, if you see blood in your urine, or if you have new swelling in one leg, in your face, or with breathlessness.
Stop the herb and speak to a pharmacist or doctor if you feel dizzy, very tired, shaky or sweaty, or if you get a rash after taking it.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Ya Zhi Cao is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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