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Scientific Name(s): Baphicacanthus cusia Brem. (Thai indigo), Indigofera anil L., Indigofera suffruticosa Mill. (Guatemalan indigo)., Indigofera tinctoria (French indigo)., Isatis indigotica Fortune ex Lindl., Isatis tinctoria L. subspecies villarsii, Polygonum tinctorium, Strobilanthes cusia (Neess) Kuntze
Common Name(s): Common or Indian Indigo, Indigo naturalis, Qing dai (Traditional Chinese Medicine)

Medically reviewed by Last updated on Oct 12, 2021.

Clinical Overview


Chiefly a source of dye, indigo also has been used as a nematicide and treatment for a range of ills including scorpion bites and ovarian and stomach cancer.


There is no clinical evidence for indigo upon which dosing recommendations can be based.


Contraindications have not yet been identified.


Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.


None well documented.

Adverse Reactions

Small studies have reported phlebitis-induced colitis and pulmonary arterial hypertension in addition to other mild effects. Indigo may irritate the eyes and may cause dermatitis.


Some species are toxic and cause birth defects.

Scientific Family

  • Acanthaceae
  • Brassicaceae
  • Fabaceae (bean)


Indigofera plants are perennial shrubs that reach a height of 1 m to 2 m. The French and Guatemalan varieties differ in the shape and size of the leaflets and pods. Isatis indigotica is a biennial or perennial herb native to the Ukraine that is widely distributed in Europe and is an invasive in the United States.Kell 2013


Indigo is one of the oldest known natural dyes and is formed through fermentation of a variety of different plants. It has been used in Traditional Chinese Medicine for centuries where it is also known as indigo naturalis, or qing dai. (Gamret 2018, Chanayatht 2002) Indigo can refer to several species of Indigofera that are known for the natural blue colors obtained from the leaflets and branches of this herb.Simon 1984 It has also been obtained from Baphicacanthus cusia, Polygonum tinctorium, and Isatis indigotica.Chanayatht 2002 Before the development of synthetic aniline and indigo dyes, indigo plants were grown commercially in the East Indies and South and Central America. Indigo was a popular dye during the middle ages.Simon 1984 It has been used medicinally as an emetic; the Chinese used the plant to purify the liver, reduce inflammation and fever and to alleviate pain.Simon 1984 Extracts of I. tinctoria have been reported to have nematicide activity and the leaf and plant juice have been used to treat cancers, particularly of the ovaries and stomach.Duke 1985 In addition, the plant has been used for the treatment of numerous ailments ranging from hemorrhoids to scorpion bites.


The blue dye is produced during the fermentation of the leaves, which is commonly accomplished with caustic soda or sodium hydrosulfite.Simon 1984 A paste exudes from the fermenting plant material and this is processed into cakes that are finely ground. The blue color develops as the powder is exposed to air. Indirubin is the red isomer of the blue indigo pigment and has been isolated from B. cusia.Chanayatht 2002

Indigo dye is a derivative of indican, a glucosideDuke1985, Chanayatht 2002 component of Baphicacanthus cusia and numerous Indigofera species and this is enzymatically converted to blue indigotin.Simon 1984, Chanayatht 2002 This colorfast dye is combined with stabilizers and other compounds to produce a wide range of colorants. Today, almost all indigo used commercially is produced synthetically.

Uses and Pharmacology

Little is known about the pharmacologic effects of Indigofera species. Preliminary evidence suggests that I. tinctoria may have a protective effect against carbon tetrachloride-induced hepatotoxicity,Anand 1981 which is opposite to the hepatotoxic effect observed with other members of this genus. The related I. aspalathoides has been reported to possess anti-inflammatory activity.Amala Bhaskar 1982 A systematic review of alternative therapies for psoriasis found reasonable evidence to support a recommendation of topical indigo naturalis on a trial basis for patients with mild to moderate psoriasis. Its beneficial action is believed to result from an antiproliferative effect on keratinocytes and repair of the epidermal barrier.Gamret 2018


There is no clinical evidence for indigo upon which dosing recommendations can be based.

Pregnancy / Lactation

Information regarding safety and efficacy in pregnancy and lactation is lacking. Avoid use.


None well documented.

Adverse Reactions

Indigo appears to be a mild ocular irritant. Dermatitis is common among indigo dyers but there is no direct evidence that this is linked to exposure to the plant or dye.Duke1985 Adverse events reported in small studies include strong suggestion of phlebitis-induced colitis and reversible pulmonary arterial hypertension as well as mild liver dysfunction, abdominal pain, and headache associated with administration of indigo.Matsuno2018, Nishio 2018


I. spicata is recognized as a teratogen due to the presence of indospicine. Indospicine also is hepatotoxic.Liener 1980, Hegarty 1988 In animals, it causes cleft palate and embryo lethality.Evans 1989 I. endacaphylla (creeping indigo) has been responsible for livestock poisonings and deaths.Simon 1984


Amala Bhaskar E, Ganga N, Arivudainambi R, et al. Anti-inflammatory activity of Indigofera aspalathoides Vahl. Indian J Med Res 1982;76(Suppl):115.7185752
Anand KK, Chand D, Ray Ghatak BJ, et al. Histological evidence of protection by Indigofera tinctoria Linn. against carbon tetrachloride induced hepatotoxicity — an experimental study. Indian J Exp Biol 1981;19:298.7251073
Chanayatht N, Lhieochaiphant S, Phutrakul S. Pigment extraction techniques from the leaves of Indigofera tinctoria Linn. and Baphicacanthus cusia Brem. and chemical structure analysis of their major components. CMU J. 2002;1:2.
Duke JA. Handbook of Medicinal Herbs. Boca Raton, FL: CRC Press, 1985.
Encyclopedia of Life. Isatis tinctoria. Updated April 2013. Accesssed October 2018.
Encyclopedia of Life. Strobilanthes cusia. Accessed October 2018.
Evans WC.Trease and Evans' Pharmacognosy. 13th ed. London; Bailliere Tindall, 1989.
Gamret AC, Price A, Fertig RM, Lev-Tov H, Nichols AJ. Complementary and alternative medicine therapies for psoriasis: A systematic review. JAMA Dermatol. 2018 Sep 5 [epub ahead of print].
Hegarty MP, Kelly WR, McEwan D, et al. Hepatotoxicity to dogs of horse meat contaminated with indospicine. Aust Vet J 1988;65:3373214366
Kell SP. 2013. Isatis villarsii. The IUCN Red List of Threatened Species. 2013:eT176545A7263416.
Liener IE, ed. Toxic Constituents of Plant Foodstuffs. London; Academic Press, 1980.
Matsuno Y, Hirano A, Esaki M. Possible association ofo phlebitis-induced colitis with indigo naturalis. Gastroenterology. 2018;155(2):576-577.30064721
Nishio M, Hirooka K, Doi Y. Pulmonary arterial hypertension associated with the Chinese herb indigo naturalis for ulcerative colitis: it may be reversible. Gastroenterology. 2018;155(2):577-578.30001991
Simon JE. Herbs: an indexed bibliography, 1971-1980. Hamden, CT: Shoe String Press. 1984.
Spoerke DG. Herbal Medications. Santa Barbara, CA: Woodbridge Press, 1980.


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