Isopathy prescribes the potentised identical agent, the disease product, allergen or toxin that produced the complaint, for that complaint. Tautopathy is the special case in which the agent is a conventional drug taken in material dose and given back in potency for its own ill effects. Homeopathy prescribes on the similarity of a proved medicine's symptom picture to the whole case, whatever the source of the medicine. The words are almost two centuries old and still argued over, because the nosodes sit on the boundary between them. What follows is the vocabulary, the history and the classical position on each, largely from texts readable in full on Similia, with the Organon and Lippe's 1881 paper from public-domain reprints. It is education for qualified homeopaths and serious students, not self-treatment advice for the public.
What isopathy is (and what "isopathic" means)
Isopathy is the treatment of a complaint with a potentised preparation of the very substance or disease product that caused it. The word joins the Greek isos, equal, to pathos, suffering, and its Latin motto is aequalia aequalibus curantur, equals are cured by equals, in deliberate contrast to Hahnemann's similia similibus curentur. "Isopathic" describes the prescribing logic, not the substance: the same Psorinum can be given isopathically by one practitioner and homeopathically by another.
E. A. Farrington gave the cleanest classical formulation in the lecture that opens the nosodes section of A Clinical Materia Medica, readable at Farrington's Psorinum: "Isopathy rests on the bold assertion that what causes disease, will cure it when administered in a high potency." His example: a patient who cannot eat strawberries without being made ill has the strawberry potentised and administered. He calls this "pure isopathy" and separates it from the proved nosodes, with which "we start with an experimental fact." In French the practice is isothérapie and in Italian isoterapia; the native terms have their own section below.
Auto-isopathy (auto-isothérapie) and hetero-isopathy
French practitioner usage divides the field by the source of the preparation. Auto-isopathy (auto-isothérapie) means the preparation is made from the patient's own product, a secretion, blood or urine, and given back to the same patient in potency. Hetero-isopathy means the agent comes from outside the patient: a pollen or a house-dust extract. Le Robert defines isothérapie as treatment with very small doses of the very substances that brought the disease, with isopathie as its synonym (source: dictionnaire.lerobert.com, 20 September 2026). Neither form is prescribed on a proving; the distinction is about where the material came from, not why it was chosen.
Where the idea came from: Lux, Hering, Swan and Lippe
Lux, 1833. Johann Josef Wilhelm Lux, a veterinary surgeon in Leipzig, published the isopathic doctrine in 1833 as Die Isopathik der Contagionen, the isopathy of contagions (source: de.wikipedia.org, Isopathie, 20 September 2026). Hahnemann knew it: a footnote to the introduction of the sixth-edition Organon names Lux and "his so-called mode of cure by identicals and idem, which he calls Isopathy".
Hering. Constantine Hering, who had himself proposed rabid-dog saliva and variolous matter as remedies in 1830 (Dudgeon, Lectures on the Theory and Practice of Homoeopathy, 1854, Lecture VI), took them into the proved materia medica and rejected the isopathic label for them. H. C. Allen preserves Hering's definition in the Secale chapter of the Materia Medica of the Nosodes, at Allen's Secale. A nosode, Hering says, "is the general term given to the alcoholic extracts of morbid productions, foolishly called isopathic remedies. The most useful and fully proved are Hydrophobinum and Psorinum."
Swan, New York. The high-potency nosode movement of the 1870s and 1880s is the practice both Farrington ("What I call pure isopathy is the practice proposed by Dr. S. Swan, of New York") and E. B. Nash name; Nash's Psorinum chapter in Leaders in Homoeopathic Therapeutics, at Nash's Psorinum, recalls the nosodes being "so widely proclaimed by Dr. Swan." Lippe's paper names no one but Lux, but the high-potency nosode practice it attacks is the one Farrington and Nash attribute to Swan.
Lippe, 1881. Adolph Lippe published "Isopathy: A Fatal Error" in The Homoeopathic Physician (vol. 1, 1881, pp. 528–532; the public-domain reprint is in PubMed Central). Its first sentence is the verdict: "It is a fatal error to claim isopathy to be Homoeopathy." Reported cures with unproved nosodes, he argues, show only that the substances act on the organism: "Facts alone prove nothing." He does not reject the medicines: "Psorinum was proved, and will forever remain an important curative agent, when properly applied under the law of the similars."
Hahnemann's objection: simillimum, not idem
Hahnemann's argument is the core, and it is readable in two places: one on Similia, one in the public-domain Organon.
The first is the passage from The Chronic Diseases that H. C. Allen reproduces, unsigned, at the head of his Psorinum chapter at Allen's Psorinum. Hahnemann explains why his list of antipsoric remedies contains no isopathic ones: "no isopathic remedies are mentioned, for the reason that their effects upon the healthy organism have not been sufficiently ascertained." Then the decisive move: "I call psorin a homeopathic anti-psoric, because if the preparations of psorin did not alter its nature to that of a homeopathic remedy it never could have any effect upon an organism tainted with that same identical virus." The same unsigned passage continues: "There is no intermediate degree between idem and similimum"; the terms "isopathic and æquale" can only mean simillimum, "they are not idem."
The second is the footnote to §56 of the sixth-edition Organon, in William Boericke's public-domain translation. Hahnemann treats isopathy as an attempted third mode of cure, "a method of curing a given disease by the same contagious principle that produces it", and concludes that because the virus is given highly potentised and therefore in an altered condition, "the cure is effected only by opposing a simillimum to a simillimum." Our Organon guide maps the doctrine section (§52–70) in which the footnote sits, and the law of similars has its own page.
Potentisation turns the identical into the similar. That is why the classical authors could use nosodes and still call themselves homeopaths, and why the simillimum, not the cause, is what gets prescribed. Allen's Materia Medica of the Nosodes, where the argument sits, is one of the 21 classic materia medica books free to read on Similia.
Isopathy vs homeopathy: the difference in one table
| Homeopathy | Isopathy | Tautopathy | |
|---|---|---|---|
| Basis of the prescription | Proved similarity of the whole symptom picture | Identity of the causative agent | Identity of the offending drug |
| Is the medicine proved? | Yes, by definition | Usually not; Hahnemann's stated objection | Rarely |
| Source of the medicine | Any kingdom: plant, mineral, animal, disease product, imponderable | Disease product, allergen, toxin, the patient's own material | A conventional drug |
| What chooses it | The totality of characteristic symptoms | The causal history | The drug history |
| Classical verdict | The method of the Organon | Rejected as a method by Hahnemann (§56 note), Lippe and Kent; the label rejected by Hering; the medicines kept | Not discussed by the classical authors; a twentieth-century term |
| Where it lives on Similia | The seven classical repertories and the 21 classic materia medica books | Allen's Nosodes, Paterson's Bowel Nosodes, the causation rubrics | Materia medica entries for the ill effects of mercury, quinine and other drugs, prescribed on similarity |
The table has no "better" column on purpose: the classical dispute was about which prescribing rule the profession would answer to, not whether Psorinum or Tuberculinum work.
Tautopathy: potentised drugs for their own effects
Tautopathy is the practice of removing the ill effects of a conventional drug with the same drug in homeopathic potency. Manish Bhatia's introduction defines it as removing the bad effects of conventional drugs by means of identical potentised drugs, states plainly that it is not based on similars and belongs to isopathy rather than homeopathy, and insists that a tautopathic medicine still needs definite guiding symptoms, not a drug history alone (source: hpathy.com, 2011, retrieved 20 September 2026).
The word is modern. Dudley Everitt's paper "Tautopathy" appeared in the British Homoeopathic Journal, volume 46, in January 1957 (Crossref record, 20 September 2026), and Ramanlal P. Patel's booklet What is Tautopathy?, published in Kottayam, India, by the Hahnemann Homoeopathic Pharmacy in editions listed from 1975 onwards (source: openlibrary.org, 20 September 2026), gave it a textbook.
The classical materia medica handles drug after-effects differently. Lippe records Carbo vegetabilis for the abuse of quinine and mercury, Boger lists Aurum for the abuse of mercury, Clarke lists Ledum for ailments from the abuse of alcohol. None is the offending drug; each is a proved remedy whose picture resembles the state the drug left behind, and a repertory's causation rubrics are built the same way.
Nash left the question open. Constitutional symptoms after inoculation, he argues, are as good a proving as those after a bee sting or rhus poisoning; then he asks: "If Rhus, very high, will cure rhus poisoning, why should not Syphilinum, etc., cure syphilis? Who will answer?"
Tautopathy vs isopathy
Tautopathy is a subset of isopathy restricted to conventional drugs; isopathy in the wider sense also covers disease products, allergens and the patient's own secretions. Neither is prescribed on a proving or on the totality of symptoms, which is what separates both from homeopathy in Hahnemann's sense.
Nosodes on the boundary: why Clarke, Kent and Nash prescribed them on similarity
The nosodes have their own page, nosodes in homeopathy; this section only draws the line, as three authors did first.
Clarke states the rule in his Medorrhinum chapter, at Clarke's Medorrhinum: "The nosodes may be used according to their indications in exactly the same way as other homœopathic remedies, and not merely for manifestations of the disease from which they are derived."
Kent puts the same rule at the front of his Tuberculinum lecture, at Kent's Tuberculinum. He does not use it "merely because it is a nosode", and the doctrine that anything syphilitic takes Syphilinum, anything psoric Psorinum and anything tubercular Tuberculinum "will go out of use some day; it is mere isopathy, and it is an unsound doctrine." Our guides to Tuberculinum, Psorinum and Medorrhinum read each proved picture on those terms; the shared vocabulary is in the three miasms.
Nash reports his own trial of the isopathic idea. Given on the matching history, the nosodes impressed him little: "I never found them markedly efficacious in such cases, but I have seen remarkable results from them in cases resembling, for instance, gonorrhœal, syphilitic or psoric troubles, without any history of pre-existing trouble of the kind." He adds that "the experience of many others seems to be different. I give only my own." Farrington names the tribunal before which all prescriptions must go, "experience", and gives his verdict on the proved nosodes: "Correctly applied, they are not isopathic remedies." The bowel nosodes are covered in our bowel nosodes guide.
The isopathic classics that became homeopathic remedies
The clearest "isopathy examples" are the smallpox group, and their history is that of a substance crossing the boundary. Boericke's Variolinum entry opens with its origin, used for "internal vaccination", then lists symptoms like any other remedy, with Malandrinum, "the morbid product of the grease of the horse", under relationships. Allen's Malandrinum chapter records the crossing: introduced against smallpox and the bad effects of vaccination on inferential grounds, then given "an extensive proving by W. P. Wesselhoeft, H. C. Allen, Steere Holcombe and students of Hering College, in 1900 and 1901." Clarke's Vaccininum entry makes the reverse point: beside the chronic state Burnett named vaccinosis, a sycotic disease in Clarke's reading, it records vaccinal whooping-cough cured with Thuja 30, the similar, and lists Thuja first among the antidotes of the nosode.
Imponderabilia: the other boundary
Imponderabilia are remedies made from non-material agents. They are neither isopathic nor nosodes: they are proved and prescribed on similarity, and only the pharmacy is unusual. Allen's Nosodes carries Bernhardt Fincke's proving of the X-ray; Electricitas, potentised on milk sugar "saturated with the current"; and three Magnetis chapters, the magnet as a whole and each pole, whose pathogenesis Allen takes from Hahnemann's Materia Medica Pura. Hahnemann's own magnet provings, from the second volume of Materia Medica Pura in Dudgeon's translation, are at Magnetis polus arcticus; our Materia Medica Pura guide explains how to read them.
Isopathy in other languages: Isopathie, isothérapie, isoterapia, isopatía
The words do not map one to one. German uses Isopathie for Lux's method and Tautopathie for the drug case, but in current German usage Isopathie also names the Enderlein tradition described next; the German Wikipedia entry says the term is no longer used in its original sense and is now associated with the biologist Günther Enderlein rather than with Lux (20 September 2026). French uses isothérapie and isothérapique, with isopathie as the dictionary synonym and auto-isothérapie for preparations from the patient's own material. Italian uses isoterapia and isopatia; the federation FIAMO defines isoterapia as a therapy that does not use the remedy "simile (omoios)" but the one "identico (isos)" to the present disease (source: fiamo.it, 20 September 2026). Spanish uses isopatía.
Enderlein's "Isopathie" (Sanum) is a separate tradition
Günther Enderlein (1872–1968) was a German zoologist who proposed a pleomorphic theory of micro-organisms changing form inside the body, called his preparations "isopathische Mittel" because they were held to contain the same symbionts the body depended on, and later worked as production manager at the pharmaceutical company Sanum; the German Wikipedia entry records that his theories of disease causation are today refuted (source: de.wikipedia.org, Günther Enderlein, 20 September 2026). These fungal and bacterial preparations are what many of the German results for Isopathie, and the Italian listings for isoterapia Sanum, are about. They are not Hahnemannian, not proved and not prescribed on similarity, so check which tradition a German source means before drawing any conclusion about nosodes.
How isopathy is used in practice today, and what the evidence says
Three modern practices go by the name: potentised allergens for the allergy they provoke; potentised drugs after conventional treatment, the tautopathic case; and nosode prescribing on similarity, the homeopathic case and the only one the classical authors endorsed.
The evidence on the first is thin and mostly negative. Lewith and colleagues ran a double-blind randomised controlled trial of ultramolecular potencies of house-dust-mite allergen in 242 asthmatic people allergic to the mite, published in the BMJ in 2002 (vol. 324, p. 520). Its stated conclusion is that "Homoeopathic immunotherapy is not effective in the treatment of patients with asthma" (PubMed abstract, 20 September 2026). The 2020 paper by Mazloomi and colleagues in the Journal of Asthma evaluated isopathic immunotherapy with highly diluted ovalbumin in BALB/c mice; its conclusion that the method "may be a good candidate treatment" is an animal-model finding, not a clinical result (PubMed abstract, 20 September 2026). No controlled trial of tautopathy appears among the current search results for the term.
Where a case genuinely turns on an identifiable cause, the classical tools are the causation rubrics and the nosode's proved picture matched against the totality. Potency and repetition for a nosode follow the same reasoning as for any other remedy.
Working with these categories in the repertory and materia medica
Isopathy needs only the causal history; homeopathy needs the totality, and that is a repertory job. On the Free plan the seven classical repertories are searchable with AI semantic repertory search at /repertory, so a causation typed in plain language, ailments after vaccination, complaints since a course of a named drug, want of reaction, finds the rubrics that carry it even when your wording differs from Kent's. Confirm a rubric's exact wording in the repertory before you cite it.
The sources quoted here are among the 21 classic materia medica books free to read online. Materia-medica search itself requires eligible paid access. Basic case management on the Free plan is capped at 3 new cases and 3 analyses per month. Pro adds the AI toolkit (Notes-to-Rubric, AI case analysis, live audio transcription, photo analysis), unlimited cases and analyses, and premium repertories and materia medica; AI-toolkit operations use credits. The full breakdown is in our Free vs Pro comparison, and the free account starts at free homeopathic software.
Where to go next
Three reads, in order: the nosodes guide for the class of medicines this page hands off to; the Organon guide for the doctrine section around §56; then Allen's Psorinum chapter in the free reader, linked above, because Hahnemann's whole argument sits at its head and takes five minutes in his own words.
