The treatment process: day by day
What happens from your arrival through diagnostics, preparation, the hyperthermia session itself, and recovery. A practical guide to the full treatment timeline.
Read more →Reviewed by Julian Douwes M.D., Chief Medical Officer, Klinik St. Georg
The scientific basis for whole-body hyperthermia rests on a well-documented biological property: Borrelia bacteria are thermolabile. They become structurally unstable and lose viability at temperatures above 41°C. Understanding this mechanism—and how it is applied in clinical practice—is essential to evaluating whether this treatment approach is right for you.
Core mechanism: Borrelia burgdorferi sensu lato bacteria become structurally unstable at temperatures above 41°C. At 41.6–41.8°C, they lose the cellular architecture necessary for survival and reproduction.
Three modes of action: Direct thermal destruction of bacteria, activation of the immune system through heat shock protein production, and enhanced antimicrobial synergy through increased membrane permeability.
Published research: The thermolability of Borrelia has been documented in laboratory research, including work by Reisinger et al. and other investigators studying spirochetal heat sensitivity.
Why whole-body: Lyme disease is a systemic infection. Only whole-body hyperthermia raises core temperature throughout all tissues—including joints, the nervous system, and deep connective tissue where Borrelia colonize.
The foundation of hyperthermia treatment for Lyme disease is a well-characterized biological property of the Borrelia genus: thermolability. This term describes an organism's vulnerability to elevated temperatures—specifically, the point at which heat disrupts the protein structures and membrane integrity that the organism needs to survive.
Borrelia burgdorferi sensu lato—the group of spirochetal bacteria responsible for Lyme disease in Europe and North America—evolved to thrive within a narrow temperature range. In the human body, this is approximately 36.5–37.5°C. Within the tick vector, temperatures are even lower. This evolutionary adaptation comes with a vulnerability: when exposed to temperatures significantly above their survival range, these bacteria cannot maintain structural integrity.
Laboratory research by Reisinger et al. demonstrated that Borrelia burgdorferi begin to show structural damage at temperatures above 41°C. At 41.6–41.8°C—the precise therapeutic target used in clinical hyperthermia—Borrelia undergo significant structural deformation. Their characteristic corkscrew-shaped morphology breaks down. Outer surface proteins denature. The spirochetal membrane loses integrity. The organisms become non-viable.
This is not a theoretical hypothesis. It is an observable, reproducible laboratory finding. The thermolability of Borrelia has been documented independently by multiple research groups and is consistent with what is known about spirochetal biology more broadly. Treponema pallidum, the spirochete responsible for syphilis, shares a similar temperature sensitivity—which is why "fever therapy" was historically used as a treatment for syphilis before antibiotics were available, a treatment approach that earned Julius Wagner-Jauregg the Nobel Prize in Medicine in 1927.
The thermolability of Borrelia bacteria at 41–42°C is supported by published laboratory research including Reisinger et al. The clinical application of this principle—whole-body hyperthermia as a treatment for Lyme disease—is based on more than 30 years of institutional clinical experience at St. George Hospital, where over 30,000 sessions have been performed. Large-scale randomized controlled trials specifically for hyperthermia in Lyme disease have not been published. We believe in being transparent about the distinction between laboratory evidence and clinical experience.
The therapeutic target of 41.6–41.8°C is not arbitrary. It represents the intersection of two clinical considerations:
This narrow window is why precision matters. The treatment is not "getting very hot." It is a carefully calibrated elevation of core body temperature to a specific range, maintained for a specific duration, under continuous medical monitoring. The margin between effective treatment and unnecessary risk is measured in fractions of a degree.
The therapeutic target temperature. At this range, Borrelia bacteria experience severe structural disruption while human physiology remains within a manageable range under medical supervision. This temperature is maintained for approximately two hours during the treatment session.
Whole-body hyperthermia works through three complementary biological mechanisms. The first is directly supported by published research. The second and third are well-established physiological responses to core temperature elevation, applied clinically in the context of Lyme disease treatment.
When core body temperature reaches and is sustained at 41.6–41.8°C, Borrelia bacteria throughout the body are exposed to temperatures that exceed their survival threshold. This is the primary mechanism of action.
Unlike antibiotic therapy, which relies on chemical disruption of bacterial processes, thermal destruction is a physical mechanism. It does not depend on the metabolic state of the bacteria. This is particularly relevant for Lyme disease, where Borrelia are known to adopt metabolically dormant persister forms—round bodies and biofilm-associated states—that are resistant to most antibiotics. These dormant forms remain vulnerable to heat because thermolability is a structural property, not a metabolic one.
Because whole-body hyperthermia raises core temperature systemically, bacteria throughout the body are affected simultaneously—including those in deep tissue, joints, the nervous system, and other compartments that oral or IV antibiotics may penetrate poorly.
Elevated core body temperature triggers a powerful innate immune response. This is the same biological mechanism behind a natural fever—amplified and sustained under controlled conditions. During hyperthermia, several immune processes are upregulated:
Heat shock protein (HSP) production increases dramatically. HSPs serve as molecular chaperones that help the immune system identify and target damaged or foreign cells. They act as danger signals that activate dendritic cells, natural killer cells, and macrophages—all frontline defenders in the immune response to infection.
Natural killer (NK) cell activity increases significantly at elevated core temperatures. NK cells are critical to the body's ability to eliminate intracellular pathogens and cells harboring persistent infection.
Cytokine profiles shift toward a more pro-inflammatory, antimicrobial pattern. This temporary shift enhances the body's ability to mount an effective immune response against residual Borrelia and co-infecting organisms. The inflammatory response resolves as the body cools, but the immune "reset" can have lasting effects on immune function.
In the Augmented Antimicrobial Therapy (AAT) protocol used at St. George Hospital, hyperthermia is combined with concurrent IV antibiotic administration. This combination produces a synergistic effect through a well-understood physical principle: heat increases cell membrane permeability.
As Borrelia cell membranes become destabilized by thermal stress, they become significantly more permeable to antimicrobial agents. Antibiotics that might have limited effectiveness against structurally intact bacteria—or that struggle to penetrate the protective barriers of biofilm communities—gain substantially improved access when bacterial membranes are compromised by heat.
This synergy means that the combined effect of hyperthermia plus antibiotics is greater than either intervention alone. The thermal stress makes bacteria more vulnerable at the same moment that concentrated antimicrobial agents are circulating in the bloodstream. It is a coordinated, simultaneous assault on the infection from two complementary directions.
This is one of the most common questions we receive, and the distinction is medically critical. Lyme disease is a systemic infection. After the initial tick bite, Borrelia bacteria disseminate through the bloodstream and colonize tissues throughout the body. They have documented tropism for joints, connective tissue, the peripheral and central nervous system, the heart, and other organ systems. This wide dissemination is precisely what makes Lyme disease so difficult to treat—and why localized heat approaches are insufficient.
The distinction is not one of degree; it is one of kind. A sauna heats your skin. A hot bath raises your surface temperature. Neither can raise the temperature deep inside your knee joints, your spinal cord, or your brain to the 41.6°C threshold required to affect Borrelia. Only a controlled whole-body hyperthermia procedure, performed in a hospital setting with medical equipment designed for this purpose, can achieve and sustain the core temperature elevation needed for therapeutic effect.
The hyperthermia sessions are performed using the Heckel HT3000, a certified medical device specifically designed for whole-body hyperthermia. This is a water-filtered infrared-A (wIRA) heating system that delivers penetrating infrared radiation to raise core body temperature in a controlled, gradual manner. Unlike older approaches to induced fever therapy, the HT3000 allows precise temperature management—the rate of warming, the plateau temperature, and the cooling phase can all be controlled with clinical precision.
The device has been in use at St. George Hospital for over two decades and has been the platform for over 30,000 hyperthermia sessions. It is not an experimental prototype. It is an established medical instrument used daily in clinical practice.
One of the most significant challenges in treating chronic Lyme disease is the ability of Borrelia bacteria to adopt persister forms. These are metabolically dormant variants of the organism that are highly resistant to conventional antibiotic therapy. Research has identified several persister phenotypes:
These persister forms are believed to be a major reason why some patients continue to experience symptoms after standard antibiotic courses. The antibiotics may eliminate actively replicating bacteria in the bloodstream while leaving dormant persisters intact in tissue reservoirs.
Hyperthermia addresses this problem through a fundamentally different mechanism. Thermolability is a structural property, not a metabolic one. Heat does not need bacteria to be actively dividing or metabolizing in order to cause damage. The thermal disruption of membrane integrity and protein structure occurs regardless of the organism's metabolic state. A dormant round body is just as vulnerable to thermal denaturation as an actively spiraling spirochete—because the heat is physically dismantling the structures that maintain the organism's viability.
This property of hyperthermia is not theoretical. It is the logical extension of the same thermolability data demonstrated by Reisinger et al. The temperatures that disrupt Borrelia structure do so based on the physical properties of the organism's membranes and proteins—properties that do not change when the organism enters dormancy.
Beyond its direct effects on Borrelia, whole-body hyperthermia produces a profound recalibration of the immune system. Many patients with chronic Lyme disease have been ill for years. During that time, their immune systems often enter a state of dysregulation—simultaneously overactive in some pathways (producing chronic inflammation) and suppressed in others (failing to effectively clear infection).
Hyperthermia appears to disrupt this maladaptive pattern. The intense physiological stress of sustained core temperature elevation triggers what clinicians describe as an immune "reset"—a period during which the immune system is forced into a heightened state of activation that can break through established patterns of tolerance or suppression.
These immune effects are not specific to Lyme disease. They are well-characterized physiological responses to hyperthermia that have been studied extensively in the context of oncology, where hyperthermia is an established adjunctive treatment. The application of these principles to Lyme disease is based on clinical observation and institutional experience rather than Lyme-specific controlled trials.
Understanding the science is important. But what matters most is what it means in practical terms.
Whole-body hyperthermia is not a wellness treatment, a sauna session, or an experimental concept. It is a medical procedure with a defined physiological rationale, performed in a hospital, under anesthesia, with continuous monitoring. The scientific basis—Borrelia thermolability, immune activation, antimicrobial synergy—provides the reasoning behind the treatment. The clinical experience of over 30,000 sessions and 12,000+ Lyme patients provides the practical foundation.
That said, we want to be honest about what the science does and does not tell us:
We believe you deserve to understand both the strength and the limitations of the evidence. Making an informed decision about your health requires honest information, not overstated claims.
If you would like to understand more about what the treatment process actually looks like day by day, continue to our treatment process guide. If you want to understand whether you may be a candidate, start with our eligibility criteria.
A case review is a no-commitment first step. Submit your medical history and symptoms, and our medical team will evaluate whether hyperthermia-based treatment is appropriate for your situation.
What happens from your arrival through diagnostics, preparation, the hyperthermia session itself, and recovery. A practical guide to the full treatment timeline.
Read more →Honest outcome reporting across 12,000+ patients. Three tiers of response, factors that influence outcomes, and the timeline for improvement.
Read more →Hyperthermia works best within a comprehensive protocol. Learn how it integrates with antimicrobials, immune support, apheresis, and nutritional rehabilitation.
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