Earth, Endotoxin, and the Humoral Body: What Traditional Farming Knew
How Galenic constitutional medicine and modern immunology converge on the body’s need for the living earth
Beneath the south-east quadrant of the parcel designated D478 in Clugnat, Creuse, at approximately eighty centimetres depth, lie the remnants of a Roman hypocaust system — the underfloor heating of a structure long since absorbed by the village’s geology. The tiles were recorded in the Bilan Scientifique Régional for Nouvelle-Aquitaine in 2020.¹ Their presence speaks of a continuous human relationship with this ground: Gallic, Roman, Carolingian, medieval, and now modern, each people working the same soil, their hands in the same earth, their bodies calibrated by the same microbial world.
That calibration is the subject of this essay: earth endotoxin.
Two converging bodies of evidence — one from twenty-first-century immunology, one from a medical tradition stretching back through the Carolingian monasteries to Galen of Pergamon — point to the same conclusion: the human body requires sustained, intimate contact with the living earth to maintain its constitutional balance. When that contact is severed, the consequences are not merely poetic. They are measurable, immunological, and serious.
The Galenic Framework: Earth as Constitutional Anchor
Galenic medicine — systematised in the second century, preserved through the Islamic medical tradition, transmitted to the Latin West through the translations of Constantine the African at Monte Cassino in the eleventh century, and codified in the monastic herb gardens and physic practices of the Carolingian period — understood the human body as a dynamic equilibrium of four humours: blood (hot and moist), yellow bile (hot and dry), black bile (cold and dry), and phlegm (cold and moist). These humours corresponded to the four classical elements — air, fire, earth, and water — and to four constitutional types whose balance or imbalance produced health or disease.
The earth quality — cold and dry, associated with black bile and the melancholic constitution — was understood not merely as a metaphysical category but as a real physiological principle of stability, groundedness, and structural integrity. Rembert Dodoens, the Flemish physician whose Cruydt-Boeck of 1554 remains one of the foundational texts of Carolingian-adjacent herbal medicine, consistently framed plant actions in terms of their ability to restore humoral balance — and the earth quality, as the principle of consolidation and binding, was understood to counter the excessive moistness and looseness that characterised the phlegmatic excess common in cold, damp climates.²
Nicholas Culpeper, working in the English tradition in the mid-seventeenth century, brought the same framework into vernacular practice, understanding the cold and dry earth principle as the corrective to dissolution, to the body’s tendency toward slack, watery disorder when deprived of the consolidating force the earth element provided.³
What neither Dodoens nor Culpeper could articulate — because the vocabulary did not yet exist — was the mechanism by which the earth’s consolidating force was transmitted to the body. That vocabulary is now available. It is the language of toll-like receptors, innate immune signalling, and microbial calibration.
The New England Journal Study: A Natural Experiment
In 2016, Stein, Hrusch, Gozdz, and colleagues published in the New England Journal of Medicine a study that constitutes one of the most elegant natural experiments in modern immunology.⁴ The researchers compared two American farming communities — the Amish of Indiana and the Hutterites of South Dakota — whose similarities are extraordinary and whose differences are, for the purposes of this argument, precisely controlled.
Both communities trace to Central European Protestant origins — the Amish to Switzerland, the Hutterites to South Tyrol — both emigrating to North America in the eighteenth and nineteenth centuries and remaining reproductively isolated since. Their lifestyles converge on nearly every variable known to influence asthma risk: large sibships, high vaccination rates, diets rich in fat and salt and raw milk, low obesity rates, extended breastfeeding, minimal tobacco smoke exposure, taboos against indoor pets.
They differ in one significant respect: farming practice. The Amish work single-family dairy farms by traditional methods, using horses for fieldwork, living in close proximity to their animals, their homes open to the biological world of the farm. The Hutterites farm industrially, on large communal operations, at a technological and physical remove from the living environment of their fields.
Earth ~ Endotoxin
The immunological consequences are striking. Asthma prevalence among Amish schoolchildren: 5.2%. Among Hutterite children: 21.3%. Allergic sensitization: 7.2% versus 33.3%. Median serum IgE — the immunological marker of allergic reactivity — was three times higher in Hutterite children.⁴
The researchers measured endotoxin levels in household dust — endotoxin being the lipopolysaccharide component of gram-negative bacterial cell walls, a reliable proxy for the density of microbial life in an environment. Amish homes showed median endotoxin levels 6.8 times higher than Hutterite homes. Microbial community composition also differed significantly between the two populations’ dust samples.
Crucially, when dust extracts from Amish homes were administered intranasally to mice sensitized to develop experimental allergic asthma, the mice were substantially protected — reduced airway hyperreactivity, reduced eosinophilia, reduced allergen-specific IgE. Hutterite dust extracts provided no such protection, and in some measures exacerbated the allergic response. The protective effect of Amish dust required functioning innate immune signalling pathways: mice deficient in MyD88 alone showed reduced protection; mice deficient in both MyD88 and Trif — key molecules at the convergence of multiple innate immune pathways — showed complete abrogation of protection.⁴
The researchers identified significant differences in the proportions and phenotypes of innate immune cells between the two populations. Amish children showed higher proportions of neutrophils and lower proportions of eosinophils. Their neutrophils bore markers suggesting recent emigration from the bone marrow — the signature of a system actively responding to microbial stimulus. Their monocytes showed a suppressive phenotype: lower expression of HLA-DR, higher expression of the inhibitory molecule ILT3 — the immunological signature of a system that has been sufficiently exposed to microbial stimulus that it has learned, at the cellular level, to modulate its own reactivity.⁴
Gene expression analysis revealed 1,449 genes upregulated in Amish peripheral blood leukocytes compared to Hutterite, with the most significant network — centred on TNF and IRF7 as hubs — being the innate immune response network. Notably, TNFAIP3, encoding the enzyme A20, was among the genes more highly expressed in Amish children; A20 is a ubiquitin-editing enzyme that limits the activity of inflammatory pathways dependent on NF-κB, and has separately been shown to mediate the protective effects of European farm dust in murine asthma models.⁴
The mechanism, in summary: sustained, dense microbial exposure from traditional agricultural environments calibrates innate immune function, reducing the allergic hyperreactivity that characterises the modern epidemic of asthma and atopic disease. The Amish children’s immune systems are not primitive or unprotected. They are, in the most precise sense, well-educated.
The Earthing Literature: Electromagnetic Calibration
A parallel and distinct body of research proposes a second mechanism by which contact with the physical earth may modulate human physiology. The proposal, developed most systematically by Chevalier, Sinatra, and colleagues, is that the earth’s surface carries a mild and stable negative electrical charge, maintained by the global atmospheric electrical circuit and by lightning activity worldwide.⁵ The human body, when insulated from the earth by rubber-soled footwear, synthetic flooring, or elevated living, accumulates a positive charge relative to the earth’s surface — a condition that may, the researchers propose, contribute to chronic low-grade inflammation by creating an electron-deficient environment in which free radical activity is unchecked.
Direct skin contact with the earth — bare feet on soil, stone, grass, or sand — allows electron transfer from the earth’s surface into the body. These free electrons are proposed to act as natural antioxidants, reducing the free radical burden that is a known driver of chronic inflammatory states. Pilot studies have reported effects on cortisol rhythms, heart rate variability, inflammatory markers including C-reactive protein, pain levels, and sleep quality in small samples.⁵,⁶
This research is preliminary and contested. The proposed mechanisms require more rigorous investigation, and the studies to date are small. They are noted here not as established science but as a convergent line of inquiry pointing in the same direction as the immunological work: the human body evolved in continuous, intimate contact with the physical earth, and systematic disconnection from that contact may carry physiological costs that were invisible so long as disconnection was partial rather than, as it has become for most of the industrialised world, nearly total.
Friluftsliv and the Developing Body
The Scandinavian tradition of friluftsliv — literally ‘free air life’ — and the forest kindergarten movement that emerged from Denmark and Germany in the mid-twentieth century represent a third convergent line of evidence, operating through neurological rather than immunological mechanisms.⁷
Children raised with regular access to unstructured outdoor environments — including, importantly, permission to get genuinely dirty, to handle soil and mud and living creatures — demonstrate measurable differences in stress regulation, cortisol patterning, executive function, and what developmental psychologists call intrinsic motivation: the capacity for self-directed inquiry that is foundational to intellectual life. Research comparing forest kindergarten cohorts with conventional indoor-schooled children has found consistent advantages in attention, risk assessment, and adaptive behaviour in the outdoor cohorts.⁷,⁸
The mechanism here is distinct from both the innate immune calibration described by Stein et al. and the proposed electromagnetic effects of earthing, but the underlying logic is the same: the developing body — immune system, nervous system, endocrine system — requires calibrated challenge from the physical world to set its regulatory parameters correctly. Deprive it of that challenge, and the system defaults to hypersensitivity: allergic in the immune domain, anxious and attentionally dysregulated in the neurological domain.
What Carolingian Farming Embodied
The Capitulare de Villis, issued under Charlemagne circa 795–800, is best read as a document about the disciplined management of biological abundance.⁹ Its seventy plants — many of them medicinal, all of them cultivated in direct, intimate relationship with the soil of the villa economy — presuppose a peasant population whose daily labour placed their hands, their feet, their bodies in sustained contact with the living microbial world of the farm.
The children of Carolingian villa farms would have grown up in environments whose endotoxin profiles resembled those of the Amish homes studied by Stein et al. far more closely than they resembled the environments of modern European children. They were, in the terminology that would not exist for another twelve centuries, in continuous innate immune calibration. Their constitutions, in the Galenic sense, were being grounded — literally and figuratively — by the earth quality of their daily existence.
The monastic physic garden, perhaps the most concentrated locus of Carolingian botanical knowledge, was itself a site of this calibration. The monks and lay brothers who worked those gardens, who turned compost and divided roots and harvested the dew-wet herbs at dawn, were, without knowing it, maintaining the innate immune education that the tradition around them encoded in the language of constitutional balance.
The earth-cold-dry of the Galenic system was, among other things, a description of what it felt like to be a body properly calibrated by contact with the living ground: consolidated, stable, neither over-reactive nor torpid, the phlegmatic excess that accumulates in bodies deprived of earthly stimulus kept in check by the daily discipline of work in and with the soil.
Modern immunology has provided the mechanism. The Galenic tradition had long provided the observation.
A Note on the Local Archaeology
The Roman hypocaust tiles at D478 in Clugnat’s south-east quadrant mark more than a structural remnant. They mark a point of continuity in the human relationship with this particular piece of earth. The Gallic peoples who preceded the Roman presence, the Romans who built the structure, the Carolingian-era inhabitants who farmed above its ruins, the medieval and modern villagers who have worked this ground since — all were, without exception, in the kind of continuous contact with the living soil that modern immunology now identifies as essential to immune health.
The century in which that continuity was most thoroughly broken — the twentieth, with its antibiotics, its concrete, its industrial agriculture, its rubber-soled shoes and climate-controlled interiors — is also the century that produced the epidemic of allergic and atopic disease that now affects a substantial proportion of children in the industrialized world.
The relationship is not coincidental.
©2026 Carolyn Smith-Kizer
Notes
1. Bilan Scientifique Régional, Nouvelle-Aquitaine, 2020, p. 181. Parcel D478, commune of Clugnat, Creuse. Roman hypocaust tile fragments recorded at approximately 80 cm depth.
2. Rembert Dodoens, Cruydt-Boeck (Antwerp: Jan van der Loe, 1554). On the elemental qualities of plants and their constitutional applications, passim.
3. Nicholas Culpeper, The English Physitian Enlarged (London: Peter Cole, 1653). On cold and dry simples and their application to phlegmatic and moist conditions, passim.
4. Michelle M. Stein, Cara L. Hrusch, Justyna Gozdz, et al., ‘Innate Immunity and Asthma Risk in Amish and Hutterite Farm Children,’ New England Journal of Medicine 375, no. 5 (2016): 411–421. doi:10.1056/NEJMoa1508749.
5. Gaétan Chevalier, Stephen T. Sinatra, James L. Oschman, Karol Sokal, and Pawel Sokal, ‘Earthing: Health Implications of Reconnecting the Human Body to the Earth’s Surface Electrons,’ Journal of Environmental and Public Health (2012): 291541. doi:10.1155/2012/291541.
6. James L. Oschman, Gaétan Chevalier, and Richard Brown, ‘The Effects of Grounding (Earthing) on Inflammation, the Immune Response, Wound Healing, and Prevention and Treatment of Chronic Inflammatory and Autoimmune Diseases,’ Journal of Inflammation Research 8 (2015): 83–96. doi:10.2147/JIR.S69656.
7. Peter Bentsen and Fiona Stein, ‘Udeskole: Outdoor Schooling in Denmark,’ Education 3–13 28, no. 1 (2000): 51–58. See also the broader friluftsliv literature in Scandinavian educational research.
8. Angela J. Hanscom, Balanced and Barefoot: How Unrestricted Outdoor Play Makes for Strong, Confident, and Capable Children (Oakland: New Harbinger, 2016), particularly chapters 2 and 4 on sensory integration and outdoor play.
9. Capitulare de Villis vel Curtis Imperii, c. 795–800. On the botanical provisions, see John Harvey, Mediaeval Gardens (London: Batsford, 1981), 26–34.