Cantharides
Spanish fly; Lytta
- Known today as
- The dried blister beetle Lytta vesicatoria.
- Kind
- Animal, in 4 older authorities
- Constituents
- cantharidin
- Poisoning
- Cantharidin poisoning
- Earliest authority here
- The Marquis de Sade
- In other databases
- GBIF search · Wikidata search
Revised October 3, 2026: Tradition, lore, modern assessment, and sources extended. Checked against its sources, each read in full, in part, or in its abstract. Version 1, first published September 25, 2026.
Deadly. Deadly by mouth.
Cantharides: what was it used for?
Blistering plasters to draw out disease, and, disastrously, an aphrodisiac.
Cantharides: what does modern science say?
Cantharidin raises blisters and harms the kidneys; a purified form was approved in 2023 for a viral skin infection. By mouth it erodes and bleeds the gut, brings blood into the urine, and can fail the kidneys, and fatal doses run from 10 to 60 mg. The same blistering, put to use, lifts off warts and molluscum: a 0.7 per cent solution was approved in the United States in 2023 for molluscum contagiosum in patients aged two and older.
Cantharides: is it poisonous?
Yes, and it can kill. Deadly by mouth. Its poisoning is cantharidin poisoning: Minutes to hours. Historical description, not medical advice; in a poisoning, call a poison centre.
Pharmacognosy & Toxicology
- Constituents
- Mechanism
- Cantharidin inhibits protein phosphatases 1 and 2A, and so loosens the skin’s cells from one another: the blister.
- Checked against ChEMBL
- cantharidin: Measured, as the entry says (“inhibits protein phosphatases 1 and 2A”): Serine/threonine-protein phosphatase 2A catalytic subunit alpha isoform (human), IC50 160 nM, CHEMBL5226315; Serine-threonine protein phosphatase 2A regulatory subunit (chicken), IC50 200 nM, CHEMBL1135579.
- Toxic dose
- Fatal by mouth at 10 to 60 mg; 1.5 to 3 g of beetles, about five, can kill.
- Syndrome
- Cantharidin poisoning
- Standing
- A 0.7 per cent topical solution approved in the United States in 2023 for molluscum contagiosum.
- Moed, L., et al. (2001). Archives of Dermatology 137. Verified against its record · doi:10.1001/archderm.137.9.1145
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.
What Medicine Makes of It
- Binding, Ligature, and ImpotenceThe knotted cord, and psychogenic impotence.
Cantharides: what lore surrounds it?
The blistering plaster of cantharides, Pomet says, was always kept ready compounded by the apothecaries, and the London Emplastrum Epispasticum of 1653 took whole cantharides; Culpeper commends it for drawing blisters in the neck for the toothache or for rheums in the eyes. The emperor Henry IV and the empress Livia are said to have used it as an aphrodisiac, in accounts Scott and colleagues could not trace to primary sources; Sade was sentenced to death for secretly giving it to women, but the sentence was never carried out.
Cantharides: what did the older authorities say?
- The Marquis de Sade
- Was sentenced to death for secretly giving cantharidin to women; the sentence was never carried out.
- Dioscorides
- Gives the way of killing the beetles over the fumes of sharp vinegar and storing them, and reports that some held them to help dropsy by moving the urine, and their wings and feet to be an antidote.
- The empress Livia
- A story retold in a 2012 Scientific American article has her using cantharides at court; Scott and colleagues (2026) note that it cannot be traced to primary sources.
- Pierre Robiquet
- Isolated cantharidin, the blistering principle, in 1810, and found it a poison as fierce as strychnine.
Sources
- Dioscorides, De materia medica II. Read in part · the text read
- Moed, L., et al. (2001). “Cantharidin revisited: a blistering defense of an ancient medicine.” Archives of Dermatology 137. Abstract read · the text read
- Scott, K. A., et al. (2026). On the history, synthesis, and medicinal use of cantharidin, LB-100, and their analogs. RSC Medicinal Chemistry 17: 743–767. Read in full · the text read
- Zhang, J., et al. (2025). Cantharidin: a double-edged sword in medicine and toxicology. Frontiers in Pharmacology 16: 1644186. Read in full · the text read
- Pomet, P. (1712). A Compleat History of Druggs. London: Bonwicke et al. Read in part · the text read
- Culpeper, N. (1653). Pharmacopoeia Londinensis: or the London Dispensatory. London: Peter Cole. Text Creation Partnership edition A35381. Read in part · the text read
Verification
- Checked
- October 1, 2026, and October 3, 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
- The mechanism read against ChEMBL (ChEMBL 37): curated mechanisms and measured activity
- Every source read, in full, in part, or in its abstract, and every sentence checked against what was read (October 3, 2026)
- Sources
- 7 cited: 2 read in full, 3 read in part, 1 abstract read, 1 verified against its record. 1 with the abstract on file.
- Corrections
- None were needed.
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 25, 2026 · last revised October 3, 2026
- Chicago
“Cantharides.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified October 3, 2026. https://thethinkingpress.org/materia-medica/cantharides.
- MLA
“Cantharides.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 3 Oct. 2026, thethinkingpress.org/materia-medica/cantharides. Accessed 8 Oct. 2026.
- APA
Cantharides. (2026, October 3). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 8, 2026, from https://thethinkingpress.org/materia-medica/cantharides
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See Also
Also in Dioscorides
Caraway broth in Dioscorides · Calamine in Dioscorides · Cardamom in Dioscorides · Wormwood, oil of in Dioscorides · everything Dioscorides names →
Drawing on the same sources: Dioscorides, Scott, Pomet, Culpeper
Verdigris · Borax · Cochineal · Catmint · Burdock · the bibliography →
Nearby in the alphabet
Caper spurge (Euphorbia lathyris) · Camphor (The crystalline gum of Cinnamomum camphora) · The Caravaca cross · Caesar’s mushroom (egg-like when young and seated in a white cup) · Butterbur (of the daisy family, with huge rhubarb-like leaves in damp places)
Historical description, not medical advice.