Printed in the 1850 edition’s “A List of the Principal Diseases” as “—— (Pestilential)” under “Fevers” (the dash stands for the heading above it, or its first word); shown here as “Fevers — (Pestilential)”.
Modern reading: epidemic fevers; nearest is antimicrobial. Searched in PubMed as each plant’s Latin name with plague OR "Yersinia pestis" OR "infectious disease" OR antibacterial OR antiviral. The counts and papers are on the Concordance page.
A note on the heading
Plain sense
The fever of the pestilence: the plague, and any contagious fever that killed like it. Culpeper’s sentences treat it as a poison in the body, resisted (Borage: “to defend the heart”) and driven out by sweating in bed.
What the entries treat
10 claims, every one with a sentence, and all ten also sit under Fevers. The plague and its fever: Blue-Bottle “is very good against the plague, and all infectious diseases, and is very good in pestilential fevers”; Elecampane “resists poison, and stays the spreading of the venom of serpents, as also putrid and pestilential fevers, and the plague itself”; Wood Sorrel “very excellent in any contagious sickness or pestilential fevers”. The fever is treated as a poison to be driven out by sweat: Butter-Bur “against the plague and pestilential fevers by provoking sweat”, Pimpernel “if the party after taking it be warm in his bed, and sweat for two hours after, and use the same for twice at least”, Clove Gilliflowers “excellently good in hot pestilent fevers, and expel poison”, Stone-Crop “expels poison much, resists pestilential fevers”, Borage “to defend the heart, and help to resist and expel the poison”; Dandelion’s water “to drink in pestilential fevers, and to wash the sores”; White Lilies, “the roots being bruised and boiled in wine, and the decoction drank”.
Where the word comes from
Latin pestilentialis, from pestilentia, “plague”, from pestilens, “infected, unwholesome, noxious”. Wiktionary’s two quotations for the illness sub-sense are Donne in 1624 (“a pestilentiall sicknes”) and Gibbon in 1783 (“the contagion of a pestilential disease”).
Today’s words
plague (the disease of Yersinia pestis); epidemic fever; contagious fever — a broad match: the heading covers more than this, or several modern things.
How it reads today
“Pestilential” has gone figurative (a pestilential nuisance). The plague itself is now one named disease, caused by the bacterium Yersinia pestis, in three forms: bubonic in the lymph nodes, pneumonic in the lungs, septicaemic in the blood. The old heading was wider than that disease, since any deadly contagious fever was pestilential, and nothing in the sentences tells which was which. The poison-and-sweat physiology is Culpeper’s, with no modern counterpart.
References
Wiktionary, s.v. “pestilential” (accessed 2026-10-28): from Latin pestilentialis, from pestilentia; sense “of or relating to pestilence or plague”, with sub-senses for people, places and substances “producing, spreading, promoting or infected with pestilence” and for illnesses “spreading in the manner of pestilence”; quotations Donne 1624 “a pestilentiall sicknes”, Gibbon 1783 “the contagion of a pestilential disease”; figurative sense “causing irritation or annoyance”. Wiktionary, s.v. “pestilence” (accessed 2026-10-28): from Latin pestilentia “plague”, from pestilens “infected, unwholesome, noxious”; sense “any epidemic disease that is highly contagious, infectious, virulent and devastating”. Wikipedia, “Plague (disease)” (accessed 2026-10-28): “Plague is an infectious disease caused by the bacterium Yersinia pestis”; “There are three forms of plague”: “pneumonic plague infects the lungs”, “bubonic plague affects the lymph nodes, making them swell”, “septicemic plague infects the blood”.
ThinkDeep333, 2026-10-28 · draft, not yet checked. Offered beside Culpeper’s heading, never in its place; nothing here says whether a plant works.
Old claims, quoted verbatim: not medical advice. A warning sits above the claims and never hides them; no warning does not mean safe, only that no source here has flagged the plant.
10 claims: 10 with a sentence, 0 from the index alone
The leaves and roots are to very good purpose used in putrid and pestilential fevers, to defend the heart, and help to resist and expel the poison, or the venom of other creatures:
being boiled in wine and given to drink, it is a good remedy against the plague, and other pestilential fevers, if the party after taking it be warm in his bed, and sweat for two hours after, and use the same for twice at least.
Wood Sorrel serves to all the purposes that the other Sorrels do, and is more effectual in hindering putrefaction of blood, and ulcers in the mouth and body, and to quench thirst, to strengthen a weak stomach, to procure an appetite, to stay vomiting, and very excellent in any contagious sickness or pestilential fevers.