Educational information, not medical advice — ask your doctor or midwife.
Osuyu is the dried, unripe fruit of a small tree in the citrus family. It is used as a single drug (Korean). The Latin name is Tetradium ruticarpum; it is also known as evodia fruit (Soeumin).
Korean medicine calls it a warming herb. It is given for belly pain that feels cold and eases with heat. It is also used for nausea, vomiting, some headaches, and cold hands and feet.
The human proof is thin. The plant has been used for many centuries in East Asia, but good trials of the fruit on its own are missing. A long history of use is not proof that a herb works.
No one has shown how Osuyu works in the human body.
Lab work points to two bitter compounds, evodiamine and rutaecarpine. In test tubes they act on TRPV1, a sensor on nerve cells that reacts to heat and chilli. That may be why the fruit tastes hot and why old texts call it warming.
Animal studies suggest it can calm the gut, ease vomiting and change blood flow. Animals are not people. Treat all of this as a clue, not a fact.
One effect is better mapped. Rutaecarpine speeds up CYP1A2, a liver enzyme that clears many drugs. Most of that work is in cells and animals, but it is the main reason to take the drug warnings below seriously.
The plain dried fruit is the base form. It is boiled in water to make a bitter decoction (a strong tea).
You may also meet it as:
Granules or powder made from a boiled extract. Small pills. A part of ready-made formulas such as Osuyu-tang (known as Goshuyu-to in Japan).
Much of the fruit sold is processed first, often soaked in licorice water. This is done to make it less harsh on the stomach. It is rarely sold as a stand-alone supplement in the West.
Osuyu has a long and wide record in East Asia. It appears in the Shang Han Lun, a Chinese text from about 200 CE, as Wu Zhu Yu.
Korean doctors took it up early. It is listed in the Donguibogam of 1613, Korea's best-known medical book.
Later Sasang medicine gave it mainly to the Soeumin type. That is a body type seen as having a cold, weak stomach. Japanese Kampo medicine uses it too.
Stop taking it and see a doctor the same day if your skin or the whites of your eyes turn yellow, your urine goes dark, or you get pain under your right ribs. These can be signs of liver trouble.
Also see a doctor if you get a rash, ongoing vomiting, or if the problem you are treating gets worse.
Get emergency help now if you have chest pain, trouble breathing, swelling of the face or throat, vomiting blood, or black tarry stools.
See a doctor first, not this herb, for a sudden severe headache, a headache with weakness or confusion, belly pain with fever, or weight loss you cannot explain.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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