Red Light Therapy (RLT) and an Infrared Sauna (IRS) both use energy from the non-ionizing light spectrum, but they are fundamentally different in their mechanisms and intended effects. The common confusion arises because both utilize forms of infrared radiation. However, RLT is a non-thermal, targeted cellular treatment, while an IRS is a thermal, systemic whole-body treatment. Understanding the specific light wavelengths and resulting physiological responses is necessary to distinguish between these popular wellness modalities.
Understanding Red Light Therapy
Red Light Therapy (RLT), scientifically known as photobiomodulation (PBM), uses specific, narrow bands of light to stimulate cellular activity without generating significant heat. Devices emit light in the visible red spectrum, typically around 630 to 700 nanometers (nm), and the invisible near-infrared (NIR) spectrum, often between 700 and 850 nm. These particular wavelengths are absorbed by chromophores within the body’s cells, primarily a molecule called cytochrome c oxidase located in the mitochondria.
This absorption process enhances the efficiency of the cell’s energy production cycle, leading to increased synthesis of adenosine triphosphate (ATP). ATP is the primary energy currency of the cell. With more available energy, cells can better perform functions like repair, regeneration, and reducing inflammation in the treated tissue. RLT devices deliver a high-intensity, focused dose of light directly to a localized area of the body. The treatment is non-thermal; if a device produces significant heat, it is not considered true photobiomodulation.
Understanding Infrared Saunas
An Infrared Sauna (IRS) is a thermal system designed to raise the body’s core temperature and induce therapeutic sweating, offering a whole-body experience. These saunas use heaters that emit infrared radiation, which is absorbed by the body as radiant heat. This systemic heat stress promotes cardiovascular conditioning, increased circulation, and muscle relaxation.
Full-spectrum infrared saunas emit a broad range of the infrared spectrum, including near-infrared (NIR), mid-infrared (MIR), and far-infrared (FIR). The FIR wavelengths, which range up to 1 millimeter, are particularly effective because they are absorbed efficiently by water molecules in the body, causing deep, penetrating heat. This heating mechanism allows the sauna to achieve significant physiological effects, such as a rise in heart rate and profuse sweating, at lower ambient air temperatures compared to a traditional sauna.
The Fundamental Difference: Light Versus Heat
The fundamental distinction between RLT and IRS lies in their primary therapeutic goal and mechanism of action—cellular stimulation versus systemic heating. RLT is classified as a non-thermal treatment, where light photons directly trigger a biochemical response inside the mitochondria to increase cellular energy. The localized application of RLT focuses on tissue repair, pain reduction, and skin rejuvenation in a targeted area.
Infrared saunas, conversely, are thermal treatments where the primary goal is systemic heat generation, promoting a state of mild hyperthermia. The body’s response to this deep, penetrating heat drives whole-body effects like increased blood flow, cardiovascular elevation, and detoxification via sweat production. An infrared sauna is specifically designed to achieve this effect, which is the main driver of its benefits.
How Wavelengths Cause Confusion
The core of the confusion rests on the shared use of the term “infrared,” which refers to a broad segment of the electromagnetic spectrum. RLT often uses near-infrared (NIR) light, typically between 700 and 850 nm, specifically because it offers maximum tissue penetration without generating excessive heat. This NIR light is utilized for its cellular signaling properties, aiming for photobiomodulation.
Infrared Saunas also use NIR in full-spectrum models, but they rely heavily on the longer mid-infrared and far-infrared (FIR) wavelengths to create therapeutic heat. It is the FIR that is primarily responsible for the deep thermal effect that raises the core body temperature and induces sweating. The small overlap in NIR wavelengths creates a terminological link, but the sauna’s overall output is broad-spectrum, heat-generating infrared, while RLT is a highly focused, non-thermal light application.