Body Heat as Medicine: What Is Infrared Radiation and Why Does What You Wear Matter
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Why 36.5 °C is such an important number
The human body is a biochemical system in constant motion. Thousands of enzymatic reactions occur simultaneously every second, and they all have one common denominator: they are temperature-sensitive. Enzymes function optimally within a narrow temperature range around 36.5 to 37 degrees Celsius. At the correct temperature, they catalyze reactions with maximum efficiency, cells produce ATP, cellular renewal takes place, and tissue regeneration occurs.
This state is professionally called homeostasis, and maintaining body temperature within this range is one of the body's most energy-intensive functions. As soon as the temperature drops by even a single degree, the body immediately registers it. Enzymes work slower. Metabolism slows down. Cells enter an energy-saving mode. And regeneration stagnates.
This is not a theory. It is physiology that manifests every day in how you feel, how quickly you recover, how well you sleep, and how efficiently your body works with energy.
What happens in the body when it is cold
Hypothermia of the body, even chronic mild hypothermia that most people don't even realize, has cascading consequences for the entire organism.
Blood vessels constrict. Through vasoconstriction, a natural reaction to cold, the body protects vital organs by restricting blood flow to the periphery. This results in cold hands and feet, a feeling of heaviness in the legs, and swelling caused by impaired lymphatic drainage. Cells in the tissues receive less oxygen and fewer nutrients, while the removal of metabolic waste products is slower.
The immune system functions less efficiently. It is no coincidence that the body raises its temperature during an infection. Fever is not a disease; it is a defense mechanism: at higher temperatures, immune cells multiply faster, viral and bacterial enzymes function less effectively, and the body's natural defenses are more active. A chronically hypothermic body is therefore more susceptible to infections and slower to defend itself.
Fat metabolism and energy balance are also temperature-dependent. A warm body is a metabolically active body. Adipose tissue at a higher physiological temperature responds better to movement and metabolic signals. Conversely, cold signals the body to enter an energy-saving mode, store energy, and slow down processes.
The nervous system perceives warmth as safety. Warmth activates the parasympathetic nervous system, the part of the autonomic nervous system responsible for rest, digestion, and regeneration. Cold and stress, on the other hand, activate the sympathetic nervous system, a state of readiness and survival. The correct body temperature therefore directly affects sleep quality, hormonal balance, and the body's ability to regenerate.
What is far infrared radiation and why the body knows it
The light spectrum is wider than we can see. Infrared radiation lies beyond visible red, and its specific part, far infrared radiation (FIR), has a wavelength between 4 and 14 micrometers.
This range is not accidental. The human body itself emits thermal energy precisely within this range. Every living cell naturally emits FIR radiation as a byproduct of metabolic activity. FIR radiation is therefore literally the natural language of body cells.
When FIR radiation penetrates tissues, it interacts with water molecules in cells in a specific way: it causes them to resonate, a process called micro-clustering, where water molecules become better organized and more biologically available for cellular processes. This results in better hydration at the cellular level, support for enzymatic activity, improved microcirculation in capillaries and the lymphatic system, and relief of muscle tension.
It is precisely this property of FIR radiation that infrared saunas and various rehabilitation technologies utilize. And it is this principle that underlies CI Fiber technology in Peu à Beauté clothing.
How CI Fiber works: physics in every fiber
CI Fiber is a special fiber containing micro-ceramic particles integrated directly into the fabric structure. These ceramic particles have a key property: they are able to absorb thermal energy radiated by the body and convert it into FIR radiation in the wavelength range biologically active for human tissues, i.e., approximately in the range of 4 to 14 micrometers.
The principle works in a closed loop: the body radiates heat, CI Fiber absorbs it, converts it into FIR radiation, and returns it to the tissues. This prevents unnecessary heat loss or overheating. A stable, biologically active thermal microclimate is created in contact with the skin, which helps the body maintain an optimal internal environment.
This technology fundamentally differs from ordinary insulating clothing. Insulating clothing merely prevents heat loss. CI Fiber actively processes heat and returns it in a biologically effective form. This is a qualitatively different approach to thermoregulation.
The premium variant of the technology, referred to as Photon fibers or Photoelectron, uses ultra-fine ceramic particles with a diameter of 0.3 micrometers with a patented optoelectronic structure for even higher absorption capacity and more efficient conversion of body heat into FIR radiation.
Peu à Beauté range: how technology works in every product
Peu à Beauté is a Japanese collection of functional clothing and accessories made in Japan from premium materials with integrated CI Fiber technology. Each product in the range has been designed to apply the technology to a specific body area with a specific functional intent.
The surface treatment of the fabrics is consistent across the entire range: shea butter, olive oil, silk amino acids, and squalane provide skin care during wear. Thus, the clothing acts not only from within through FIR radiation, but also on the skin's surface through natural moisturizing and nourishing ingredients.
Shaping and slimming briefs combine 360-degree pelvic support with CI Fiber technology. Pelvic stabilization contributes to alleviating back pain and shoulder stiffness, FIR radiation supports circulation in the hip and lower abdominal area, and helps maintain optimal body temperature. The shaping effect and functional health support coexist in one product.
Slimming corset belt is based on Power Net fabric with CI fiber and spiral reinforcements for a precise fit. FIR radiation in the waist area supports circulation, relieves muscle tension, and contributes to thermoregulation in the central part of the body, where essential metabolic processes reside.
Slimming cotton belt adds a gentle cotton surface and shea butter surface treatment to Power Net fabric and CI Fiber. It is suitable for sensitive skin and for all-day wear, where both comfort and functional thermoregulation support are desired.
Trespa leggings are designed for active wear and regeneration. Gentle targeted compression combined with CI Fiber supports blood circulation in the lower limbs, contributes to the metabolic activity of muscles, and through FIR radiation helps maintain optimal body temperature even during physical activity. The water molecule atomization technology, which is part of the material, further supports internal cellular processes.
Night leggings for sleep use Clima Textil fiber with ceramic particles that are activated by body heat during sleep. Night regeneration is a period when the body repairs tissues, consolidates immunity, and processes metabolic processes. FIR radiation in nightwear supports deep muscle relaxation, stabilizes the circadian rhythm, and contributes to a higher quality of regenerative sleep. Shea butter is absorbed into the skin during wear, providing hydration overnight.
Daily compression socks combine CI Fiber with ionic silver for antibacterial protection and gradual compression in the ankle and calf area. FIR radiation supports microcirculation in the legs, silver ions prevent bacterial growth, compression reduces swelling and leg fatigue. They are ideal for standing work, travel, or long journeys.
Night compression socks work with Photon fibers and shea butter for night regeneration of the lower limbs. CI fiber stabilizes the circadian rhythm and contributes to regeneration, shea butter hydrates the skin of the feet, and the compression cut reduces swelling and supports venous return.
Tank top with Photoelectron technology is the product of the highest technological range. Ultra-fine ceramic particles with a diameter of 0.3 micrometers with a patented optoelectronic structure absorb and emit FIR radiation at body temperature with exceptional precision. The lightweight fabric maintains pleasant warmth without overheating and is suitable as a base layer even during rest.
Photonic blanket transfers CI Fiber technology into a relaxing format. Warmed by body heat, it absorbs some energy and converts it into FIR radiation, which gently returns to the skin surface. The result is even warmth and mild microcirculation stimulation. It is ideal for resting, during cosmetic procedures, while traveling, or at work.
A scientific basis that speaks for itself
FIR radiation and its biological effects on tissues have been the subject of scientific research since the 1990s. Studies have repeatedly confirmed its ability to promote vasodilation and microcirculation, stimulate cellular metabolism through water molecule resonance, contribute to muscle tension relief, and reduce inflammatory markers in tissues with prolonged exposure.
CI Fiber technology makes this effect accessible in everyday wear: without the need for a sauna, without a special device, without booking a procedure. FIR radiation works all the time the clothing is on the body, both during the day and at night.
Who is Peu à Beauté for?
The Peu à Beauté range will appeal to anyone who wants clothing to cease being just a passive layer and to actively contribute to the body's health. It is suitable for those who suffer from cold extremities, swelling, or poor circulation, for active women and men who want to support muscle regeneration after exercise, for anyone looking for better sleep quality and more natural thermoregulation, and for those who want a shaping effect combined with health care, not just an aesthetic compression effect.
The products are made in Japan from premium materials and are suitable for unisex wear in most sizes.
Explore the entire Peu à Beauté range