# Iron and steel

**Ferrum*, *chalybs**

**Known today as.** The metal, given as filings in wine, as its rust, or in chalybeate spring waters.

Kind: Mineral  
Poisoning: Mercury, arsenic, lead, and antimony (https://thethinkingpress.org/materia-medica/poisons/heavy-metal)

## What was it used for?

Against the green sickness (chlorosis) and weakness of the blood.

## What does modern science say?

It works: chlorosis was iron-deficiency anemia, and iron is still its treatment.

## Pharmacognosy and toxicology

- **ferrous sulfate**: 
- **ferrous fumarate**: 

**Mechanism.** Iron is the centre of haemoglobin; the salt is absorbed in the duodenum and the body cannot excrete an excess, so overdose corrodes the gut and then poisons the liver and heart.

**Dose.** In a child, 20 mg per kilogram of elemental iron brings symptoms, 60 mg can kill: the commonest fatal poisoning of children in the United States in the 1980s and 90s, from a parent’s tablets.

**Standing.** Ferrous salts are on the WHO list of essential medicines; iron deficiency is the commonest nutritional disorder in the world.

## What lore surrounds it?

Cold iron was the old defense against fairies and witches: a knife under the threshold, a horseshoe over the door.

English legend gives the horseshoe over the door to Saint Dunstan, a smith before he was Archbishop of Canterbury: asked by the Devil to shoe his cloven hoof, Dunstan nailed the shoe on so painfully that the Devil begged for its removal, and was released only on his promise never to enter a house where a horseshoe hung. Iron railings around graveyards carried the same logic in reverse, keeping the dead in rather than evil out.

## What did the older authorities say?

**Thomas Sydenham.** Prescribed steel for the green sickness, one of the few remedies of his age that did exactly what it claimed.

## Sources

- Sydenham, T., *Works*, on chlorosis.
- Wikipedia, “Iron in folklore.”
- Centers for Disease Control (1993). “Toddler deaths resulting from ingestion of iron supplements, Los Angeles, 1992–1993.” *MMWR* 42.

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*Iron and steel.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/iron

Historical description, not medical advice.