# Woad (Isatis tinctoria)

**Isatis**

**Known today as.** *Isatis tinctoria*. A biennial of the mustard family whose fermented leaves yielded Europe’s principal blue dye before indigo.

Kind: Plant

## What was it used for?

The dominant blue dye of medieval Europe, grown on an industrial scale in England, France, Germany, and Italy; the Languedoc around Toulouse grew rich on its trade.

## What does modern science say?

A genuine historical textile dye; the war-paint legend does not survive scrutiny.

## Pharmacognosy and toxicology

- **indican and isatan B**: indigo precursors in the leaf
- **indigo and indirubin**: the dye
- **glucobrassicin**: a glucosinolate
- **tryptanthrin**: 

**Mechanism.** The leaf’s indoxyl glycosides are fermented and oxidised to indigo, the blue; indirubin from the same chemistry is the active principle of the Chinese leukaemia remedy danggui longhui wan, a kinase inhibitor, and the root (ban lan gen) is the most used antiviral of the Chinese pharmacopoeia, with laboratory activity and weak trials. The plant is not psychoactive and the Britons’ war paint is Caesar’s one sentence.

**Dose.** Safe.

**Standing.** A dye plant; *Isatis* root and leaf are in the Chinese Pharmacopoeia.

## What lore surrounds it?

The popular claim that the ancient Britons and Picts painted themselves blue with woad for battle rests on Julius Caesar’s report that the Britons dyed themselves with *vitrum*, a word that more often means “glass” than “woad,” and the woad reading may owe more to the interests of early modern woad growers than to Caesar. Lindow Man, the preserved Iron Age body sometimes cited as evidence, in fact bore a copper- or iron-based pigment, and modern experiments have found woad too caustic to tattoo. Its real history is commercial rather than martial: it lost its dominance only when indigo arrived from the New World in the sixteenth century.

## What did the older authorities say?

**Pliny.** Woad enters the Natural History as body paint. “There is a plant in Gaul, similar to the plantago in appearance, and known there by the name of ‘glastum:’ with it both matrons and girls among the people of Britain are in the habit of staining the body all over, when taking part in the performance of certain sacred rites; rivalling hereby the swarthy hue of the Æthiopians, they go in a state of nature.”

**Culpeper.** A cold and dry plant of Saturn; some affirm it destructive to bees; “the herb is so drying and binding, that it is not fit to be given inwardly”; an ointment of it stanches bleeding, a plaster over the spleen takes away its hardness, and it quenches St Anthony’s fire.

## Sources

- Wikipedia, “*Isatis tinctoria*.”
- Pliny the Elder, *Natural History* 22.2, trans. J. Bostock & H. T. Riley (1855), Perseus Digital Library.
- Culpeper, N. (1653). *The Complete Herbal*, “Woad.” Project Gutenberg #49513.
- Hoessel, R., et al. (1999). “Indirubin, the active constituent of a Chinese antileukaemia medicine, inhibits cyclin-dependent kinases.” *Nature Cell Biology* 1.
- Speranza, J., et al. (2020). “*Isatis tinctoria* L. (woad): a review of its botany, ethnobotanical uses, phytochemistry, biological activities, and biotechnological studies.” *Plants* 9.

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*Woad.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-01. The Thinking Press. https://thethinkingpress.org/materia-medica/woad

Historical description, not medical advice.