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Herb library · Herb · Acorus calamus

Calamus (sweet flag)

An aromatic marsh plant whose root has been used in traditional medicine worldwide, now banned by the FDA from use in food. Its asarones cause liver cancer in rodents, and people who took calamus products to get high had prolonged vomiting.

Serious warning

The FDA prohibits calamus, calamus oil and calamus extract in human food (21 CFR 189.110). The EMA reports that its asarones are genotoxic and cause liver cancer in rodents, and Swedish poison-center cases of calamus intoxication involved vomiting that sometimes lasted more than 15 hours.

Traditional use

The rhizome has been used in traditional medicine worldwide, for stomach cramps, dysentery, asthma and worms and as a tonic and stimulant (EMA). In India it was long sold in the bazaars for children's bowel complaints, and Hindu medicine considered it an emetic in large doses and a tonic in small ones. Dutt's 1877 compilation from Sanskrit medical works, which names it Vachá, records it in powders for indigestion with asafetida, pepper and ginger, and in mixtures for fevers, epilepsy and insanity. In recent years calamus products have been sold online as hallucinogens. In North America, Melvin Gilmore recorded (1919) that the Dakota, Omaha, Ponca, Winnebago and Pawnee held it in very high esteem, chewing the rootstock for coughs, toothache and colds; among the Chippewa (Ojibwe), Frances Densmore recorded (1928) that it was measured out by the length of the patient's finger because it was so strong.

What studies show

  • Insufficient

    Digestion, asthma and other traditional uses: no controlled studies in people were found. What is known in people is harm: 30 cases of intentional calamus intoxication reported to Sweden's national poisons information service in 2003 to 2006.

Be careful of

Cautions

  • AmountThe EMA set a temporary limit for asarone in herbal medicines of about 115 micrograms a day (about 2 micrograms per kg of body weight) and says asarone should be kept to a minimum.
  • NoteAsarone content varies hugely by variety: the rhizome oil of the Asian tetraploid type is 85 to 95% beta-asarone, while the American diploid type contains none detected.
  • NoteProducts sold as hallucinogenic contain asarones but, in the Swedish tests, no trace of the amphetamine-like compound claimed to be the active ingredient.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

From the old books

What herbals and dispensaries of the past printed. History, in their words.

“The aromatic rhizome or root-stock of Acorus Calamus is considered emetic in large doses, and stomachic, carminative and nervine in smaller doses.”
Udoy Chand Dutt, The Materia Medica of the Hindus (1877), p. 251. See the page of The Materia Medica of the Hindus, p. 251 (opens in a new tab) · Read the full passage from The Materia Medica of the Hindus, p. 251
“All the tribes hold this plant in very high esteem. It was used as a carminative, a decoction was drunk for fever, and the rootstock was chewed as a cough remedy and as a remedy for toothache. For colic an infusion of the pounded root stock was drunk.”
Melvin Randolph Gilmore, Uses of Plants by the Indians of the Missouri River Region (1919), pp. 69–70. See the page of Uses of Plants by the Indians of the Missouri River Region, pp. 69–70 (opens in a new tab) · Read the full passage from Uses of Plants by the Indians of the Missouri River Region, pp. 69–70
“Thus one root (calamus), although only about one-eighth of an inch in diameter, was so strong that the quantity used was measured by the length of the patient’s index finger, whether an infant or an adult.”
Frances Densmore, Uses of Plants by the Chippewa Indians (1928), pp. 328–329. See the page of Uses of Plants by the Chippewa Indians, pp. 328–329 (opens in a new tab) · Read the full passage from Uses of Plants by the Chippewa Indians, pp. 328–329

In scripture

Where the Bible names this plant, and which plant scholars think is meant.

spikenard and saffron, calamus and cinnamon, with every kind of incense tree; myrrh and aloes, with all the best spices,
Song of Solomon 4:14, World English Bible

The calamus of Scripture is the fragrant cane of Exodus 30:23. Balfour (1885), following Royle, identified it as an aromatic Indian grass (Andropogon calamus-aromaticus), not the sweet flag (Acorus calamus) on this page; the two share a name, calamus, which means reed. John Hutton Balfour, The Plants of the Bible (1885), p. 137 (opens in a new tab)

Sources

  1. Substances Added to Food: CALAMUS--PROHIBITED (opens in a new tab) · FDA · read September 25, 2026
  2. Public statement on the use of herbal medicinal products containing asarone (EMEA/HMPC) (opens in a new tab) · EMA · read September 25, 2026
  3. Bioanalytical investigation of asarone in connection with Acorus calamus oil intoxications (2009) (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.