The dose makes the poison: what Paracelsus really said

“The dose makes the poison” is the short form of a sentence by the Swiss physician Paracelsus (1493-1541) that is now taught as the basic principle of toxicology: any substance can do harm if the amount is large enough, and many poisons heal in the right amount.¹ Paracelsus wrote it in German in 1538, and what it says is slightly different: “all things are poison and nothing is without poison; only the dose makes a thing not a poison”.² The previous article told of the search for gold; Paracelsus is the alchemist who said alchemy was not for that. Here is the sentence in the original, which I read in Karl Sudhoff's edition, the quarrel it was written in and what it means today.

Who said “the dose makes the poison”?

Paracelsus, whose name was Theophrastus Bombast von Hohenheim. According to Wikipedia, Paracelsus was born in Einsiedeln, Switzerland, in 1493; was city physician of Basel in 1527, lecturing in German rather than Latin and publicly burning a copy of Avicenna's Canon; and died in Salzburg in 1541.¹ The name “Paracelsus” first appears in 1529, and its meaning is uncertain: either a Latinisation of Hohenheim, or “beyond Celsus”, the Roman physician.¹

The sentence is in a little book of self-defence, the Seven Defences (Septem Defensiones). According to Sudhoff, Paracelsus dated its preface at Sankt Veit, in Carinthia, on 19 August 1538; it was printed first in Latin, in Strasbourg in 1566, and the German original came out in Cologne, in the first edition by the heirs of Arnold Byrckmann.² It is the third defence, titled “on account of writing new recipes”.

The original sentence, in German

Here it is as Sudhoff prints it, read from the image of the page because the digitised text of the blackletter type is illegible:²

wenn ir iedes gift wolt recht auslegen, was ist das nit gift ist? alle ding sind gift und nichts on gift; alein die dosis macht das ein ding kein gift ist. als ein exempel: ein ietliche speis und ein ietlich getrank, so es uber sein dosin eingenomen wird, so ist es gift; das beweist sein ausgang.

In English: “if you would interpret every poison rightly, what is there that is not poison? All things are poison and nothing is without poison; only the dose makes a thing not a poison. For example: any food and any drink, if taken beyond its dose, is poison; its outcome proves it.”

A few lines earlier it is said another way: “it is neither too much nor too little. Whoever hits the middle receives no poison” (es ist nicht zu vil noch zu wenig. der das mittel trift der entpfecht kein gift).² The idea has two sides: excess does harm, and what is held to be poison does none in its measure.

And “sola dosis facit venenum”?

The Latin version, sola dosis facit venenum, “only the dose makes the poison”, is the one quoted as if it were Paracelsus's own, but Paracelsus wrote in German. I could not find who coined that Latin form, and I did not read the 1566 Latin translation. What a comparison does show is that the motto turns the sentence around: Paracelsus says the dose makes something not a poison, which is a defence of the remedy; the motto says the dose makes the poison, which is a warning. Both follow from the same idea.

Why it was written: a defence

The sentence does not come from a calm treatise but from a quarrel. Critics accused Paracelsus of giving poisons as medicine, and the third defence answers by hitting back. It asks the critics which purge in their books is not poison “or does not serve to kill” if the dose is not considered “in its right weight”; it reminds them that their own theriac, the great remedy of the age, is made with the viper, and the viper is poison.²

Then it turns to mercury, which is what the argument was really about: “you know that mercury is nothing but poison, and daily experience proves it”, and yet you smear the sick with it “much harder than a cobbler greases leather with tallow”, fumigate them with its cinnabar, wash them with its sublimate, “and will not have it said that it is poison, though it is poison” (ir reuchent mit seinem zinober, ir waschet mit seinem sublimat und wöllet nit, das man sag es sei gift das doch gift ist).² According to Wikipedia, the great medical problem of the time was syphilis, and Paracelsus had attacked the fashionable remedy, guaiac wood, as useless.¹ The argument is that everyone used poisons; the difference lay in knowing how to correct and measure them.

This piece goes through the passage sentence by sentence:

What does “the dose makes the poison” mean today?

In toxicology, that the harm a substance does depends on how much of it reaches the body. According to Wikipedia, even water and oxygen are toxic in excess, and a poisonous plant such as foxglove gives digoxin, a medicine, in small controlled doses; the limits for contaminants in water and food are set on that principle.³

Two things the sentence does not say. First, that everything is safe in small amounts. For some substances no safe threshold is known; the WHO writes of lead that “there is no level of exposure to lead that is known to be without harmful effects”.⁴ Second, that diluting something makes it stronger. Paracelsus is sometimes quoted in defence of homeopathy, but what the sentence says is the opposite: the effect depends on the amount. And a warning, because the text speaks of mercury, cinnabar and sublimate: these were treatments of five centuries ago, they are toxic, and nothing in this article is medical advice.

Paracelsus and alchemy: the stomach is the alchemist

Paracelsus was an alchemist, but not of gold. In the Paragranum of 1530, alchemy is the third of the four pillars of medicine, explained with an image: when you take a remedy, “the stomach must prepare it for you, and it is the alchemist”. The physician's alchemy is then “the outer stomach”, and the text says: “not as they say, that alchemy makes gold, makes silver; here the purpose is: make arcana and direct them against diseases” (nicht als die sagen, alchimia mache gold, mache silber; hie ist das fürnemen mach arcana und richte dieselbigen gegen den krankheiten).⁵ Arcana are, for Paracelsus, the hidden virtues and powers in things that heal. It is the turn that made alchemy a chemistry of medicines, and the reason Paracelsus is sometimes called the father of toxicology.¹

What I could not read

In Sudhoff's edition I read the third defence, the editor's introduction on its date and editions, and a passage of the treatise on alchemy in the Paragranum; not the other six defences nor the whole Paragranum. Sudhoff prints the German in the spelling of the old editions; I replaced the long “ſ” with “s”. I did not read the 1566 Latin translation or the first German edition, nor find the origin of the form sola dosis facit venenum. The biography comes from Wikipedia, which also notes that many writings were falsely attributed to Paracelsus; the third defence, according to Sudhoff, is genuine. I am not a Germanist: the translations are mine and could be improved.

What we do with this

Paracelsus asked for the right weight to be checked before a remedy was judged. At Anima Mundis, the Observatory gives quantities, how many voices and at what hour, not adjectives. It is a modest form of the same lesson: before saying whether something is a lot or a little, count it.