Epsom salt
Sal catharticum; bitter salt
- Known today as
- Magnesium sulfate, first boiled from the waters of a spring on Epsom Common in Surrey.
- Kind
- Mineral, in 1 older authority
- Constituents
- magnesium sulfate
- Earliest authority here
- Nehemiah Grew
- In other databases
- Wikidata search
Epsom salt: what was it used for?
A purge, sold across Europe from the 1690s; bathed in, and drunk at the wells.
Epsom salt: what does modern science say?
Still a laxative. Given into a vein, magnesium sulfate prevents seizures in eclampsia of pregnancy, and it is used in severe asthma.
Pharmacognosy & Toxicology
- Constituents
- Mechanism
- By mouth the salt holds water in the bowel; into a vein, magnesium blocks calcium channels and NMDA receptors and stops the seizures of eclampsia, where the Collaborative Eclampsia Trial (1995) showed it beat diazepam and phenytoin and the Magpie trial (2002) showed it beat placebo.
- Toxic dose
- Magnesium poisoning from enemas and from laxative abuse in kidney failure: weakness, a slowed heart, and stopped breathing.
- Standing
- On the WHO list of essential medicines for pre-eclampsia and eclampsia.
- Altman, D., et al. (2002). “Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial.” Lancet 359. Verified against its record · doi:10.1016/s0140-6736(02)08778-0
Constituent names open the compound’s record at PubChem, and “ChEMBL” beside a name opens its record at ChEMBL, the European Bioinformatics Institute’s database of bioactive molecules. Where a mechanism line was checked against ChEMBL (ChEMBL 37, read 1 October 2026), the check is shown with the measured value and its source paper, or says plainly that nothing has been measured. Doses are as the references give them, for description only; this is not medical advice. Each source carries the result of its check against Crossref, PubMed, or the authority’s page: see Verification.
Epsom salt: what lore surrounds it?
The story goes that in 1618 a farmer named Henry Wicker found his cows refusing the bitter water of a spring on the common, though they were thirsty; the water became famous for its purging.
Epsom salt: what did the older authorities say?
- Nehemiah Grew
- Obtained the salt from the water and took out a patent for making it in 1698.
Sources
- Grew, N. (1695). Tractatus de salis cathartici amari in aquis Ebeshamensibus. Book, not indexed
Verification
- Checked
- October 1, 2026
- Passes
- Every sentence read against its sources, in the pass over the remaining 343 entries
- The Standing line checked against the authority it names (EMA, WHO, FDA, CITES, Commission E)
- Every dated or regulatory claim checked by category across the database
- Sources
- 2 cited: 1 verified against its record, 1 book, not indexed.
- Corrections
- the Magpie trial (2002) beat placebo; the Collaborative Eclampsia Trial (1995) beat diazepam and phenytoin. The entry had merged them.
What was checked, how, and what was found is set out on the Verification page. A checked source is one whose record was found; it does not make the entry medical advice.
Cite This Entry
Version 1 · first published September 30, 2026
- Chicago
“Epsom salt.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified September 30, 2026. https://thethinkingpress.org/materia-medica/epsom-salt.
- MLA
“Epsom salt.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 30 Sept. 2026, thethinkingpress.org/materia-medica/epsom-salt. Accessed 8 Oct. 2026.
- APA
Epsom salt. (2026, September 30). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 8, 2026, from https://thethinkingpress.org/materia-medica/epsom-salt
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See Also
Nearby in the alphabet
Ergot · Epithymum (Cuscuta epithymum, a parasitic plant) · Eryngo · Epiphany water (in the East as the Great Blessing of the Waters at Theophany) · The exorcists’ manuals (above all those of the Franciscan Girolamo Menghi) · Epiphany chalk · The eye bead (white, light blue, and black, like an eye) · Endive (the salad plant)
Historical description, not medical advice.