Educational information, not medical advice — ask your doctor or midwife.
Lengua de vaca is a roadside weed, Rumex crispus, called curly dock in English. In Latin American home medicine the root was used for sluggish bowels, skin rashes and "weak blood". The young leaves are also cooked and eaten as a green.
Two things about this plant matter most. The root holds compounds that loosen the bowel. The leaves and stems hold oxalic acid, the same acid that makes rhubarb leaves unsafe to eat.
Human evidence is very thin. Almost everything claimed for it comes from tradition and from lab work, not from trials in people. Long use by many generations is not proof that it works, and it is not proof that it is safe.
The clearest proposed action is on the gut. The root holds anthraquinones, the same family of compounds found in senna. In people, that family pulls water into the bowel and speeds things along.
Dock itself has not been tested this way in people. Its anthraquinone level is lower than senna's. It also swings a lot from plant to plant, so batch strength is hard to guess.
The old idea of "cleaning the blood" has no clear mechanism. In test tubes, dock extracts slow some bacteria and fungi. Whether that happens on human skin is not known.
Lab tests also find antioxidant activity in the root and leaf. Animal work hints at effects on blood sugar and swelling. Neither finding has been confirmed in people.
Dock is often sold as an iron plant. The leaves do contain iron. But the oxalates in the same leaves bind minerals, so how much iron you actually absorb is unclear.
Dried root, loose or cut, simmered into a strong tea.
Tincture, an alcohol extract, sold in dropper bottles.
Capsules or tablets of powdered root.
Syrups, often blended with molasses and sold as an iron tonic.
Salves, creams and washes for itchy skin.
Fresh young leaves, boiled and eaten as a vegetable. This is food use, not remedy use, and the oxalate warnings still apply.
Curly dock spread with European settlement and became a common weed across the Americas. Healers in Mexico, Central America and the Andes took it up under names such as lengua de vaca and romaza.
The root was used for constipation and for stubborn skin trouble. It also had a reputation as a spring tonic for people thought to have "tired blood". Herbalists in Europe and North America used the same plant in much the same way.
The cooked leaves were eaten in hard seasons as a free green. Traditional writers often warned against eating too much at once.
Stop taking it and speak to a doctor or pharmacist if you get cramping that does not settle, diarrhoea lasting more than a day, or any new rash.
See a doctor promptly if you notice:
- Pain in your side or back - Pink, brown or very dark urine - Passing much less urine than normal - Lasting muscle weakness or cramps - Tiredness that is getting worse
Get emergency care now for severe belly pain, vomiting you cannot stop, blood in your stool, numbness or tingling in your mouth or face, muscle twitching, a fluttering or irregular heartbeat (arrhythmia), or trouble breathing. Take the product or plant with you if you can.
If you are tired and think your iron is low, ask for a blood test rather than treating it with a herb.
In the United States, curly dock root is sold as a dietary supplement. It is not approved as a drug, and claims to treat disease are not allowed.
In the UK and the EU it is sold as a food supplement or herbal product, not as a licensed medicine. The plant itself is a common weed and is not controlled.
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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