The proposed mechanism of the cure was humoral. Disease was held to be morbid or “peccant” matter in the body, and the action of cold water (applied externally and drunk in quantity) was to mobilize that matter and expel it through a “crisis.” Claridge’s 1842 account describes the crisis as the moment the disease “comes to a head” and the morbid material makes “their exit by some means or other; by diarrhoea, by urine, by boils or ulcers, or fever,” an event “hailed with the greatest joy as the harbinger of health.” The Deutsche Biographie records that Priessnitz worked from humoral-pathological views.

The mechanism is recorded as refuted. It belongs to the classical humoral theory of medicine, the doctrine of the four cardinal humours and their morbid matter (Encyclopaedia Britannica, “Humour”), a pre-modern framework that scientific medicine does not employ; disease is not a material substance discharged through eruptions, and boils, diarrhoea, and fever are not the expulsion of a disease-cause. The crisis doctrine is also unfalsifiable as stated: because any acute symptom is counted as the morbid matter leaving the body, no outcome could ever disconfirm it. What persists in modern practice is a small set of cold-water-application techniques with limited, separately evidenced effects, not the morbid-matter mechanism.