Did King Henry I die from poison instead of eating lampreys?

Medieval Poisons

King Henry I died of eating a surfeit of lampreys … but was it poison instead?

King Henry I died in Normandy in 1135 of food poisoning “according to legend from eating a ‘surfeit of Lampreys’ (an eel type fish).”  http://www.britroyals.com/kings.asp?id=henry1

In the new mini-series on Starz “Pillars of the Earth” based on the book by Ken Follett, he was deliberately poisoned by King Stephen (who succeeded him) or someone working for him.  For those watching the show, in point of fact, King Henry did not die within moments of the birth of Maud’s son, Henry (born 5 March 1133), who ultimately succeeded Stephen as King of England, but two years later.

King Henry died of food poisoning despite the high likelihood of having some kind of ‘food taster’.  Admittedly, such a person could be circumvented by a slow-acting poison.  In addition, in regular food poisoning, the effects are not felt for up to 24 to 48 hours, although 4-6 is also common.  Either way, a taster would not have been an effective stop to poisoning.

“The heavy burden of preventing poisoning appears was spread amongst a veritable platoon of servants, from the head cook to the lowliest server, each with the responsibility for specific and often repeated steps for ensuring that their liege lord did not succumb to a poisoning attempt. In The Art of Cookery in the Middle Ages, Scully describes a lengthy process for ensuring the master’s food was safe…

“Everything that was intended for the prince’s mouth became subject normally to two general sorts of tests, called assays: on the one hand, a test by means of a unicorn horn[crazy as it sounds], and on the other, a test by what vulgarly we might today call guinea-pig experimentation. This second sort of test needs no long explanation: it derived from the principle that one should oneself be willing to stand the salubrity of what one offers to others while making the claim that it is perfectly harmless….Clearly the test assumed that any poison effective enough to do in the prince — merely harming him could very readily prove in short order to be fatal to the poisoner instead! — would become manifest quickly and plainly enough to spare the prince the danger of ingesting it.”  http://www.katjaorlova.com/HerbalismPaperAntidotes.html

The most common poisonous herbs in the Middle Ages were belladonna, hemlock, monkshood/wolfsbane, and foxglove.

Belladonna (Deadly Nightshade):  “Its deadly character is due to the presence of an alkaloid, Atropine, 1/10 grain of which swallowed by a man has occasioned symptoms of poisoning. As every part of the plant is extremely poisonous, neither leaves, berries, nor root should be handled if there are any cuts or abrasions on the hands. The root is the most poisonous, the leaves and flowers less so, and the berries, except to children, least of all. It is said that an adult may eat two or three berries without injury, but dangerous symptoms appear if more are taken, and it is wiser not to attempt the experiment. Though so powerful in its action on the human body, the plant seems to affect some of the lower animals but little. Eight pounds of the herb are said to have been eaten by a horse without causing any injury, and an ass swallowed 1 lb. of the ripe berries without any bad results following. Rabbits, sheep, goats and swine eat the leaves with impunity, and birds often eat the seeds without any apparent effect, but cats and dogs are very susceptible to the poison.

Belladonna is supposed to have been the plant that poisoned the troops of Marcus Antonius during the Parthian wars. Plutarch gives a graphic account of the strange effects that followed its use.” http://www.botanical.com/botanical/mgmh/n/nighde05.html

Hemlock:  “Poison Hemlock can grow to be about 6 to 10 ft. tall. It has leaves and white flowerheads resembling those of parsnips, carrots, and water hemlock. It has a fleshy, white taproot, a main stem with characteristic light red spots and a disagreeable smell. All plant parts are poisonous. However, the seeds contain the highest concentration of poison. The conium alkaloids are volatile and can even cause toxic reactions when inhaled.”


Monkshood/Wolfsbane (Aconite):  “All the species contain an active poison Aconitine, one of the most formidable poisons which have yet been discovered: it exists in all parts of the plant, but especially in the root. The smallest portion of either root or leaves, when first put into the mouth, occasions burning and tingling, and a sense of numbness immediately follows its continuance. One-fiftieth grain of Aconitine will kill a sparrow in a few seconds; one-tenth grain a rabbit in five minutes. It is more powerful than prussic acid and acts with tremendous rapidity. One hundredth grain will act locally, so as to produce a well-marked sensation in any part of the body for a whole day. So acrid is the poison, that the juice applied to a wounded finger affects the whole system, not only causing pains in the limbs, but a sense of suffocation and syncope.

Some species of Aconite were well known to the ancients as deadly poisons. It was said to be the invention of Hecate from the foam of Cerberus, and it was a species of Aconite that entered into the poison which the old men of the island of Ceos were condemned to drink when they became infirm and no longer of use to the State. Aconite is also supposed to have been the poison that formed the cup which Medea prepared for Theseus.” http://botanical.com/botanical/mgmh/a/aconi007.html

Foxglove:  “In 1775 an English doctor named William Withering (1741-1799) began studying the foxglove plant. He learned that an effective medicine for treating heart ailments could be made from drying leaves picked just before the plant blossomed and crushing them into a powder. Withering also discovered that this medicine, digitalis—one of a number of substances called found in the plant—could be poisonous if the patient was given too much. Withering was aware that digitalis was effective only in certain forms of dropsy (edema), but apparently did not associate this with the cardiac actions of the drug. Withering published his findings about digitalis in 1785, but in spite of his warnings about proper dosage, many doctors prescribed the medicine in doses that were too large and for sicknesses it could not cure.

The active principles of digitalis were not known to researchers until the mid-1800s, when two French scientists, Homolle Ouevenne and Theodore Ouevenne, found the substance digitalin in the foxglove plant. In 1875 Oscar Schmiedeberg (1838-1921) identified the potent chemical digitoxin in the plant, and in 1930 the English chemist Sydney Smith obtained the medicine used today, digoxin, from the wooly foxglove plant, Digitalis lanata.

Today doctors know that if too much digitalis enters the circulatory system the patient may experience nausea, vomiting, trouble with vision (seeing too much yellow or green), and a very slow and irregular heartbeat. A larger amount of digitalis can result in convulsions (severe seizures) and death. Even grazing animals that eat too much of the foxglove plant can become poisoned by its glycosides.” http://www.discoveriesinmedicine.com/Com-En/Digitalis.html

Read more: Digitalis – used, anesthetic, blood, body, produced, plant, Foxglove, The Pharmacy in the Garden, Witherings Studies http://www.discoveriesinmedicine.com/Com-En/Digitalis.html#ixzz0vTQf40z4

23 Replies to “Medieval Poisons”

  1. this is so helpful! I’m writing a story about assassins right now, so something like this is extremely useful. I do have some questions, for each of these, do you know about how long it would take for the poison to kill someone?

    1. Few are truly instant. Some take hours to even days, depending on the dose. Probably a further googling of the ones that interest you would reveal the specifics!

  2. Hi, Sarah! For my book, I have a character who has ingested poisons since he was a child to build somewhat of a tolerance to them. He’s trying to assassinate someone by poison and to maintain his innocence, he’ll take the poison (hidden in food) at the same time as the other person who doesn’t have any tolerance. I’ll need something that
    – has a range (ie too much equals death and just enough can be remedied by an antidote)
    – something that can become less effective with repeated exposure.

    Which poison would be advisable for this?

    Also should my character take the antidote before or after he ingests it given that he would have somewhat of a tolerance?

    Thank you!

    1. I appreciate your wanting to do this, but I really am not an expert on poisons. There would also have to BE an antidote, which there isn’t for most herbal poisons. You might be better off inventing something that was synthesized in a lab, or, given that your character appears to have been training to be an assassin since childhood, an herb you made up that is known only to whatever organization he’s working for. Best of luck to you!

    2. Arsenic is your poison. Anecdotally, people have deliberately ingested arsenic in order to build tolerance (see stories around the Borgias and Rasputin)

  3. Hi, Sarah, thanks so much for this article. I write historical fiction set in 15c Italy. I want to use the terms Foxglove, or Dead Man’s Bells, Monkshood, and so on, but those terms were not used then. The Latin terms, perhaps, but that is not nearly as exciting. How do you handle this? Ellis Peters, in her Cadfael series, just goes ahead and says monkshood…much appreciated!

    1. Because Ellis Peters goes ahead and uses it, I thinks that’s license to do so too. And really, just because the first use is 1548 doesn’t mean it wasn’t referred to as such long before then. Those names would certainly be more in line with the common tongue than the Latin. For Monkshood, you could also use Wolf’s bane https://en.wikipedia.org/wiki/Aconitum

    2. I just found this: “Aconite is now found wild in a few parts of England, mainly in the western counties and also in South Wales, but can hardly be considered truly indigenous. It was very early introduced into England, being mentioned in all the English vocabularies of plants from the tenth century downwards, and in Early English medical recipes.” https://botanical.com/botanical/mgmh/a/aconi007.html

      Sounds to me like you can use it … the title of the article is ‘Monkshood’

  4. Sarah, for my book – I’m looking for an herb that someone in the Middle ages may have used to commit suicide. Of course, death is not a pleasant side-effect, but I’m looking for a milder one. Meaning, an herb that doesn’t cause nausea, vomiting, seizures, or anything too unpleasant for my characters.


    1. Well … if they drank enough poppy juice (opium), they’d just go to sleep and never wake up. I don’t know of another off the top of my head!

  5. I hope you don’t mind me asking, Sarah, but which poison would be easiest to hide in food, causing nausea and diarrhoea but not death? The easiest one I’ve found for my next book is the Fool’s Funnel toadstools, but I’m wondering if one of the above would work better

  6. Great post! Researching medieval life in Europe generally and Wales in particular. This site is fantastic. Thank you.

  7. thank you sooooo much!!! See in school we have to do this medieval project and your site helped me sooooo much!!!

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