I cannot help but pay attention to how things actually work, not the way a polished salesperson says they work. If the wood on a fence holds through winter, you know why it holds. If a horse spooks, you track the sound or movement that triggered it. If a calf is not gaining weight, you adjust feed, water, or pasture until the physiology makes sense. Tracing cause and effect has served me well in medicine. It also makes me persistent when explanations feel incomplete.
Over the past few years, I noticed more and more friends talking about infrared saunas and how remarkable they are. These are thoughtful, educated people. Physicians. Entrepreneurs. Athletes. They speak about detoxification, mitochondrial activation, improved circulation, and cellular repair. The language is confident. The benefits are presented as an established fact. When I ask where they learned this, the answer is usually the same. The company that sold them the sauna explained it.
I am not satisfied when someone tells me a therapy is safe because it is all natural or because it carries a scientific label. I want to know how it works. I want to know what happens at the tissue, blood flow, protein structure, and cellular signaling levels. I want to understand the mechanism before I accept the promise.
So I started with something simple. Heat.
We have been heating our bodies for as long as we have controlled fire. We understand fire. Wood burns. Combustion releases energy as heat, evidenced by reality. We stand by a fire, and we get warm. The metal of a stove absorbs the heat energy and becomes hot. When you touch the metal, heat transfers directly into your skin. When you stand near the stove, the air around you warms. The room gradually increases in temperature. Your skin warms first. Blood vessels at the surface dilate. Warmed blood circulates inward. Cooler blood returns outward. Over time, core temperature rises because the environment around you is warmer than your body temperature.
That is direct heat transfer. The problem is that the cult of science has once again reduced the observable to a cartoon world and adds complication where, as I argue in this article, it is unnecessary. Before we move on to radiation, we need to be clear about what heat is.
What Is Heat, and Do We Need the Atomic Story?
The Standard Working Definition
In physics, heat is defined as energy transferred from one system to another because of a temperature difference. Temperature is described as a measure of the average kinetic energy of particles in a substance. When molecular motion increases, temperature rises. When molecular motion decreases, temperature falls. Molecular motion is never directly observed, only the aftereffects. This will be an important distinction later in this section.
Under standard chemical theory, materials such as wood contain what is called chemical potential energy. This energy is associated with the alleged arrangement of never observed atoms within molecules and the bonds that hold them together. Wood is largely composed of cellulose, hemicellulose, lignin, and smaller amounts of resins and other organic compounds. These molecules are said to contain carbon, hydrogen, and oxygen atoms arranged in specific structures.
In the accepted framework, combustion is an oxidation reaction. When wood burns, oxygen from the air (again, this is their story) reacts with the carbon and hydrogen in the fuel. Existing chemical bonds in the fuel are broken, and new bonds form in the reaction products, primarily carbon dioxide and water vapor. According to thermodynamic calculations, the bonds formed in these products are lower in energy than the bonds in the original fuel. The energy difference between the initial and final molecular configurations is released during the reaction.
That released energy is not described as a substance but as increased kinetic energy of the surrounding molecules. The gas molecules in the flame move faster. The solid materials are believed to vibrate more intensely. This increase in molecular motion is what they say they detect as heat and elevated temperature.
Heat output is measured through bomb calorimetry. A known mass of fuel is first dedicated and then burned in a controlled chamber surrounded by a material with known heat capacity, often water. The rise in temperature of the surrounding medium is recorded. Because the heat capacity is known, the total energy released by the fuel can be calculated. Results are expressed in joules, calories, or BTUs per unit mass. I wrote all about it here: Dropping the Bomb on the Calorimeter.
In addition to measuring temperature change, scientists measure “oxygen” consumption during combustion, the mass and composition of gases produced, pressure changes in sealed systems, and the mineral composition of residual ash. Using these measurements, they construct stoichiometric equations and energy balance models. From those models, they claim that the total heat released by a given fuel can be predicted from its potential, aka chemical composition, before it is burned.
Within this framework, wood burns not merely because it is dense or dry, but because the specific atomic arrangement of the hidden carbon (we discover it was. carbon because when we burn it we find ashes-anyone else see a problem with this) and hydrogen within its structure contains quantifiable chemical potential energy that is released when oxidized. I wrote about the Carbon Fiction here:
https://medicinegirl.substack.com/p/the-multi-trillion-dollar-carbon
But not so fast, dear science cultists, not so fast.
Do we need the never-observed-only-believed microscopic explanation in order to predict heat output in real systems?
In practical fire science and engineering, predictions rely on observable properties and controlled measurements rather than on microscopic bond diagrams. In reality, we don’t need the additional story of the atomic bonds and their stored energy. Similarly, after the laws of density, we don’t need the mythical, never-observed, never-makes-practical-sense story of gravity.
Those observable variables include:
• Mass of the fuel
• Density
• Moisture content
• Surface area
• Flammability characteristics such as ignition temperature and burn rate
• Air availability and oxygen concentration
• Confinement and airflow
• Environmental pressure and altitude
• Measured heat per unit mass
A pound of dry oak produces more heat than a pound of cottonwood because repeated output measurement shows that it does. Oak contains more combustible material per unit volume and burns for longer. Green wood burns poorly because fire and heat are diverted into evaporating internal water before flammability and sustained combustion can occur. Fires at high altitude burn differently because the lower air pressure reduces flame temperature and combustion efficiency. These relationships are measurable and repeatable without reference to or need for microscopic theory.
Flammability itself is a measurable property. Materials have known ignition temperatures, critical masses, flash points, and flame spread rates. Surface area alters how rapidly air can interact with fuel. Confinement alters pressure and reaction rate. Airflow determines whether combustion is complete or incomplete. Engineers can quantify these variables directly. No atomic stories necessary. They can also routinely calculate heat release using empirical BTU/lb values derived from calorimetry. Once a fuel’s energy output per unit mass is established experimentally, the total heat release is calculated by multiplying the mass by the measured energy density, then adjusting for moisture content, oxygen availability, the flammability of the source, and burn efficiency. The practical calculation requires no atomic diagram, once again. There is a use for the ol’ bomb calorimeter after all. Just to determine the energy output of food.
Fat burns differently from cellulose based on the flammability potential. Oil in a lamp burns long and steadily because it melts, vaporizes gradually, and is metered upward through a wick. Paper burns quickly due to its high surface area and thin structure. Dried manure burns according to fiber content, moisture, and residual fat of the animal's diet. Muscle tissue burns differently from wood because of the makeup of the tissue, water, and fat distribution. These differences are observable material properties affecting flammability, burn rate, and total heat release.
Gas production can be measured directly by capturing and analyzing combustion gases. Air consumption can be measured by monitoring concentration changes in a sealed chamber. Pressure shifts can be recorded. Residual ash can be analyzed for differing mineral composition. Wood ash differs from bone ash in measurable elemental content. These determinations rely on direct mass and composition measurements after combustion.
Even explosive yield scales with the mass of reactive material under comparable confinement. Engineers predict blast energy from the known energy density per unit mass of the explosive compound. Increase the mass under similar geometric and atmospheric conditions, and total energy output increases proportionally within physical limits. These are scaling laws grounded in measurable reaction output. We don’t need the splitting of the atom to make the bomb.
From this vantage point, combustion can be modeled using macroscopic variables:
• Fuel mass and flammability
• Bulk composition at the material level
• Moisture content
• Air concentration
• Environmental pressure
• Confinement and airflow
• Empirically measured energy per unit mass
These are observable and quantifiable. Heat output can be measured directly. Gas production can be measured. Residue can be analyzed. Energy can be calculated without invoking microscopic narratives in the practical workflow.
The atomic framework may provide theoretical depth and a mysterious cult-like elegance, but for real-world prediction of burn behavior and heat release, empirical thermodynamics and flammability laws more than suffice.
Conventional Heating
In traditional heating, the mechanism is straightforward.
A fuel burns. The environment becomes hot. Air temperature rises. Objects in that environment absorb the heat because they are cooler than their surroundings. Heat flows from hotter regions to cooler regions until equilibrium is approached.
A wood stove heats the surrounding air. Heated air rises, creating movement. Skin worms and blood flow redistribute that warmth inward through the vessels. A furnace operates by raising the ambient air temperature and circulating it through an enclosed space. A warm bath transfers heat directly through contact with water that is hotter than the body. Even sunlight warms the skin by delivering energy to the surface, which then redistributes inward through circulation.
In each case, there is a measurable temperature gradient. If the environment is hotter, the body equilibrates in it.
This is the baseline understanding of heat transfer.
Infrared Heat, A Coat of Many Colors
Infrared saunas are described differently, like a coat of many colors; it is the light that heats the body from within rather than by raising ambient air temperature. The room itself may not be hot, yet users sweat and report deep warmth.
The claim is that electromagnetic waves in the infrared range travel through air and are absorbed directly by tissue. That absorbed energy is converted to heat at the point of absorption rather than first heating the surrounding air and surfaces.
This raises legitimate questions and safety concerns.
If we can model conventional combustion and heat transfer using macroscopic thermodynamics, flammability characteristics, oxygen availability, and empirical measurement, do we need to move immediately into molecular vibrational language to explain infrared exposure? Or can we first analyze it using the same observable framework: total energy delivered, tissue temperature change, exposure duration, penetration depth, and cumulative dose?
Before accepting claims of targeted internal heating, we should determine whether infrared exposure represents a fundamentally different biological interaction or simply a different method of delivering measurable energy into tissue.
Infrared Radiation and the Claim of Internal Heating
Infrared radiation is a portion of the electromagnetic spectrum just beyond visible red light. It is not visible to the human eye, but it carries energy. Any object above absolute zero emits infrared radiation as part of its thermal emission. The hotter the object, the more radiation it emits and the shorter the dominant wavelength.
Infrared sauna systems use electrically heated elements or ceramic emitters that radiate energy primarily in the near-, mid-, or far-infrared ranges. Unlike a conventional sauna, which raises ambient air temperature substantially, infrared devices emit electromagnetic waves that travel through the air and are absorbed directly by the body. Houston, I think we have a problem.
The standard explanation is this: Infrared photons strike tissue. Certain molecules in the body, particularly water and organic compounds, absorb this radiation. When absorbed, the energy increases molecular vibration. That increased vibrational motion is experienced as heat. Because the air temperature may remain lower than in a traditional sauna, proponents describe the effect as heating the body from within rather than from the outside inward. Ya, kind of exactly the way a microwave works to heat food, not the surrounding air.
Is infrared a Giant Microwave Set on Low?
Microwave radiation and infrared radiation are both electromagnetic waves. They differ mainly in wavelength and frequency, and in how they are generated and absorbed.
Microwaves in an oven are produced by a device called a magnetron. Electricity is converted into electromagnetic waves at a specific frequency, usually about 2.45 gigahertz. Those waves bounce around inside the oven's metal cavity. The metal walls reflect the microwaves, keeping the energy contained. When the waves encounter food, especially water molecules, the oscillating electric field forces those polar molecules to rotate back and forth billions of times per second. That molecular motion generates heat throughout the volume of the food where the microwaves penetrate. The oven air itself does not heat much because air absorbs microwaves poorly. Metal objects reflect microwaves and can create sparks because the electric field concentrates at sharp edges.
Infrared radiation in a sauna is formed a little differently. Electrical current heats a resistive element or ceramic panel. As that material heats up, it emits infrared radiation. No magnetron is involved. The infrared waves travel through the air and are absorbed when they strike the body. Absorption increases molecular vibration, which raises the temperature.
The similarity is this: in both cases, electromagnetic energy is converted into molecular motion, which we experience as heat. The differences are in frequency, penetration depth, method of generation, and the degree of selective energy absorption by tissue. If microwave energy can penetrate food and generate internal heating through molecular motion, and infrared energy also increases molecular motion when absorbed, then the distinction between “heating from within” and “heating from without” becomes a matter of wavelength, penetration depth, and duration.
Now we ask: how do we measure whether this is occurring? There are several observable and measurable indicators.
First, surface temperature can be measured using infrared thermography. Thermal imaging cameras detect infrared radiation emitted by the skin and convert it into temperature maps. If tissue temperature rises during exposure, it can be objectively recorded.
Second, core temperature can be measured in controlled studies using ingestible temperature sensors, rectal thermometers, or esophageal probes. If internal body temperature increases during infrared exposure without an equivalent rise in air temperature, that is measurable.
Third, local tissue temperature can be measured using implanted thermocouples in research settings. These devices can record temperature changes at specific depths beneath the skin. If deeper tissues increase in temperature during exposure, this provides direct physical evidence of energy deposition.
Fourth, the total energy delivered can be measured in watts per square meter at the skin surface. Infrared irradiance meters measure the amount of electromagnetic energy that reaches the body. Exposure time multiplied by irradiance gives total energy dose.
Fifth, physiological responses such as increased heart rate, vasodilation, sweating, and changes in blood flow can be measured. These are secondary indicators of heat stress and thermoregulatory response.
All of these measurements are observable and quantifiable, and you or I could repeat and verify them.
If infrared radiation raises tissue temperature by delivering measurable energy, then, at a thermodynamic level, it still increases molecular motion. The difference lies not in whether heat is produced, but in how the energy arrives.
With combustion heating, the environment becomes hotter, and the body equilibrates to that environment.
With infrared heating, electromagnetic energy may pass through air with less heating of the air itself and deposit energy directly in tissue.
The devil’s advocate question is not whether tissue warms. That can be measured. The question is whether the mechanism is meaningfully different in biological consequence from conventional heat exposure once total energy dose and temperature rise are accounted for.
If two methods raise core temperature by the same number of degrees for the same duration, is the physiological response identical? Or does wavelength-specific absorption create secondary effects beyond bulk heating?
That is where measurable reality must be separated from marketing language.
Before invoking mitochondrial activation, detoxification, or cellular signaling pathways, the first obligation is to quantify:
Energy delivered.
Temperature change.
Depth of penetration.
Duration of exposure.
Only once those are established can we determine whether infrared exposure represents a new biological phenomenon or a variation of an old one.
In the next section, we will examine near-, mid-, and far-infrared wavelengths individually and evaluate the experimental evidence on their penetration depths and interactions with biological tissue.
Infrared Exposure Is Not Limited to Industrial Hazards
Near-infrared radiation, also referred to as IR-A, is not confined to factories or welding shops. It is present in natural sunlight, artificial heating devices, infrared lamps, medical therapy equipment, biometric scanners, night-vision systems, and increasingly in consumer wellness devices such as infrared saunas.
More than half of the solar energy that reaches Earth is in the near-infrared. Daily sunlight exposure already includes a substantial IR-A component, but it spans the full spectrum of light, so it does not damage the way isolated, manufactured, and condensed lights do. Artificial sources add to that baseline. Infrared therapy lamps, near-infrared light panels, and sauna emitters intentionally deliver concentrated IR energy to the body.
Industrial and occupational settings such as glass blowing, steel production, and welding have historically provided clear examples of harm from chronic infrared exposure. Accelerated cataract formation in workers repeatedly exposed to high levels of IR-A has been documented. The mechanism is cumulative heating of the lens, the same way infrared works, but at a lower level of radiation. The lens has limited blood flow and limited heat dissipation, making it vulnerable to repeated thermal stress.
Retinal injury has also been documented under sufficiently intense near-infrared exposure, particularly with high-output sources such as infrared lasers or focused IR beams. IR-A penetrates through the cornea and lens more effectively than mid- or far-infrared, which are largely absorbed at the surface. That deeper penetration is precisely why IR-A is considered more hazardous to internal ocular structures.
Skin is not exempt. Chronic infrared exposure has been associated with dermal changes and premature skin aging in workers exposed to sustained radiant heat. Thermal burns can occur when exposure exceeds tissue tolerance, regardless of whether the source is industrial, solar, or therapeutic. Remember, thermal burns that occur on the inside of the body will go unnoticed.
The point is not that infrared is inherently catastrophic. The point is that it is biologically active and capable of injury under sufficient intensity or duration. The idea that harm is restricted to occupational extremes is inaccurate. Dose and duration determine outcome.
Infrared saunas and therapeutic IR devices deliberately expose the body to concentrated infrared energy. The mechanism is well understood: as the temperature rises, energy absorption, water vibrations inside the body, and sensitive organs trigger a response from tissues.
The question now becomes whether consumer devices operate at intensities and durations that remain safely below injury thresholds for skin, lens, and retina, especially with repeated use over years.
Near-infrared penetrates deeper than mid- and far-infrared. That deeper penetration may be marketed as a benefit. It is also the reason safety margins must be clearly defined.
If infrared heating is simply controlled thermal exposure, then safety must be evaluated in terms of cumulative heat dose to vulnerable tissues. If it is more than that, then evidence must demonstrate what that “more” consists of beyond heat alone.
Sunlight Is Not the Same as Concentrated Infrared
Natural sunlight is broad-spectrum. It includes visible light, ultraviolet, near-infrared, mid-infrared, and far-infrared radiation in varying proportions. The body has evolved under full-spectrum solar exposure. The eye has response mechanisms: blinking, pupillary constriction, the aversion reflex, tear-film cooling, and vascular heat dissipation. Solar exposure is diffuse and dynamic. Intensity changes with time of day, latitude, cloud cover, and atmospheric conditions.
Infrared devices are different. They emit isolated and concentrated energy within specific wavelength bands. The exposure is close range, fixed in direction, and often sustained for defined periods of time in an enclosed space.
That difference matters.
Near-infrared penetrates more deeply into ocular tissue than mid- or far-infrared radiation. The eye is not just surface tissue. Behind the cornea and lens are aqueous and vitreous fluids. The lens itself has limited vascular cooling. Repeated thermal stress to avascular structures has historically been associated with cataract formation under sufficient exposure conditions.
If infrared exposure increases vibrational energy in tissue water, then ocular fluids and lens proteins are part of that equation. Thermal energy absorbed by these structures must be dissipated. The question becomes whether repeated exposure, even at moderate levels, could produce cumulative thermal effects over time. Not a gamble I would want to take. Once your eyes are scarred, you must engage serious healing mechanisms to hopefully reverse this, or turn to the medical industrial complex for cornea implants and surgical interventions.
The issue is not whether sunlight contains infrared. It does. The issue is whether concentrated, wavelength-targeted infrared exposure in enclosed environments produces a different heating pattern than diffuse solar exposure across the full spectrum.
“Does concentration, geometry, and duration distinguish natural sunlight from engineered infrared panels?” —Captain Obvious. Which brings the captain to the only rule she lives by. “Never interfere with Mother Nature.” Sorry, biohackers, ya basic, completely wrong, and downright toxic. Sorry Ben, but the lines in your face look exactly like long-term steroid use, oh sorry I mean “peptide” use, not your biohacking fairyland. Not accusing Ben of steroid use, but his body gives me the telltale signs, and more questions deserve answers from someone who makes a living telling people what to put inside their bodies.
Safety cannot be assumed simply because the sun emits infrared radiation. The exposure context is different.
If infrared energy is absorbed by water-rich tissue that vibrates from the assault and converted into heat, then any fluid-filled structure, including sensitive ocular tissue, becomes part of the thermal equation. That requires careful quantification of intensity, duration, and cumulative exposure.
Infrared heating may be controlled and therapeutic within defined margins. It may also carry risk if those margins are exceeded.
That is not speculation. It is a thermodynamic reality.
Heat Is NOT Heat
Infrared saunas may very well deliver a controlled thermal stress. The burden of proof rests on demonstrating that wavelength-specific exposure produces benefits beyond what controlled thermal stress already provides — and that it does so without introducing cumulative risk to the eyes, skin, or deeper tissues and organs. It is non-ionizing radiation, like lightwaves, as Jeanice Barcelo has more than demonstrated, and ultrasound is extremely harmful to the developing fetus and can cause a host of downstream issues. Maybe that's why they always give infants a hearing test to determine the success of their ultrasound experiments on the yet-to-be-born public. They could easily determine when the ultrasound was performed and at what stage it was most likely to cause hearing loss in a developing baby. The human cochlea begins developing early in the first trimester, with critical structural formation and neural connections appearing around 9 to 12 weeks of gestation. The sensory epithelium begins to differentiate, with hair cells forming in the basal turn around weeks 10–12.
Knowing what I know about non-ionizing radiation, I will never set foot in an infrared sauna; I will choose the method of heat that human beings have trusted for centuries.
I will keep my saunas pure and only opt for wood-fired, Finnish saunas built the traditional way, without glues, adhesives, plastics, or chemical off-gassing. Real fire. Real heat. Real temperature gradient. If it gets too hot, I step out and jump into a lake. Talk about circulation and incredible relaxation afterwards. If I need a sweat and can’t hike at my normal pace and vigor, like I am tired and need to rest, an electric heated sauna would be an occasional treat.
And for those without a sauna at all, there is an even simpler, more natural, and much better solution.
Hike long hills wearing a long-sleeved thin wool sweater. Wool breathes and pulls sweat off the body. It insulates. It allows you to generate your own heat under your own metabolic control. If you get too warm, you remove a layer. The temperature gradient is self-regulated. You sweat through effort, not through electrical panels mounted to a wall.
If you try this, start slow and be honest about your current conditioning. Bring water the first few times and pay attention to how your body responds. Over time, your system adapts, your sweat response becomes more efficient, and your tolerance for exertional heat improves in a way that feels earned rather than artificially induced.
Heat is not mystical, and it is not harmless. It is a physiological stressor. Used intelligently, it can strengthen circulation, improve resilience, and train the body to regulate itself more effectively. Used carelessly or excessively, it can damage tissue and strain vulnerable systems. The determining factors are intensity, duration, frequency, and the level of internal pollution in your tissues' fluids.
The question is not whether we can sweat. The question is how — and at what cost.
I will choose movement, sunlight, wood fire, and wool. No warning label required.
References
International Commission on Non-Ionizing Radiation Protection. (2013). Guidelines on limits of exposure to incoherent visible and infrared radiation. Health Physics, 105(1), 74–96.
Sliney, D. H. (2006). Exposure geometry and spectral environment determine photobiological effects on the eye. Photochemistry and Photobiology, 82(2), 389–396.
Sliney, D. H., & Wolbarsht, M. L. (1980). Safety with lasers and other optical sources: A comprehensive handbook. Plenum Press.
World Health Organization. (2007). Environmental health criteria 160: Ultraviolet radiation. WHO Press.
Holmström, G., & Ericson, K. (1988). Infrared radiation and cataract formation. Documenta Ophthalmologica, 68(3–4), 333–338.
Parrish, J. A., Jaenicke, K. F., & Anderson, R. R. (1982). Erythema and melanogenesis action spectra of normal human skin. Photochemistry and Photobiology, 36(2), 187–191.
Hale, G. M., & Querry, M. R. (1973). Optical constants of water in the 200 nm to 200 µm wavelength region. Applied Optics, 12(3), 555–563.
Dewhirst, M. W., Viglianti, B. L., Lora-Michiels, M., Hanson, M., & Hoopes, P. J. (2003). Basic principles of thermal dosimetry and thermal thresholds for tissue damage from hyperthermia. International Journal of Hyperthermia, 19(3), 267–294.
ICNIRP. (2000). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Physics, 79(4), 431–440.
Schieke, S. M., & Schroeder, P. (2009). Infrared radiation and skin: Friend or foe? Experimental Dermatology, 18(12), 989–994.
Disclaimer
The views expressed in this article are the author’s opinions, based on clinical experience, historical sources, public records, and secondary reporting. Where applicable, references to peer-reviewed and archival material are provided to support discussion of physiology and public health policy.
The author is a licensed Registered Nurse (RN) no longer working in the field. This article reflects professional observation and analysis, but it is not intended as individualized medical advice, diagnosis, or treatment. Readers should consult their own licensed healthcare professionals for personal medical decisions.
This piece is written for informational and educational purposes only. It does not allege proven legal wrongdoing by any named company or individual.
If you believe this article contains a factual error, or if you represent an entity mentioned and wish to provide source documentation or request a correction, please contact robin@purifywithin.com. Corrections will be made promptly where warranted.
Nothing in this article should be construed as legal advice. For legal guidance regarding publishing, liability, or defamation, consult a qualified attorney.
