Hey there, (Frantic wave from Samantha to you!)
Fellow light therapy enthusiast! Today, I want to tackle a common myth wonderfully explained by GembaRed’s Andrew, from Gembared LLC (Video link below).
Many people believe near-infrared (NIR) light means heat. They also think red light is cooler. I’m here to tell you that’s often wrong. Let’s dig into the science together.
Is Infrared Heat a Myth? Understanding Light Therapy Basics
Where did the idea that infrared always means heat originate in light therapy? Perhaps our education linked “infrared” with “heat.” But infrared is just a specific wavelength range. How light interacts with matter matters more.
Not all infrared becomes heat. High-intensity LED devices often feel warm. People then falsely attribute this warmth to NIR light. This shows heat is not just about wavelength.
Intensity, energy, and coverage area all play a role. A tiny laser is different from a large panel. We’ll focus on wavelength today.
Red Light Therapy Safety: What Standards Reveal About Heat
What do official safety standards for red light therapy reveal about heat? Look at skin safety standards for intensity. These standards vary by wavelength. They set limits before heating or burns occur. One study cites ANSI standards. For 635 nm red, stay below 200 mW/cm². For 808 nm NIR, stay below 400 mW/cm². That’s a huge difference, isn’t it? Your skin tolerates twice as much NIR intensity. Red light at 635 nm heats twice as much as NIR.
Another photobiomodulation study references standards. For 800-900 nm NIR, stay below 750 mW/cm². For 600-700 nm red, stay below 300 mW/cm². For blue light (400-500 nm), it’s below 100 mW/cm². This means red is 2.5 times hotter than NIR.
Let’s focus on common NIR wavelengths. These are 800-900 nm and 1050-1120 nm. We are avoiding the 900s for this discussion. That range has high water absorption.
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Blue Light Therapy and Heat: A Surprising Connection
How about blue light therapy and its surprising heat contribution? Blue light causes a lot of heat. Stay below 100 mW/cm² for blue light. Blue is about three times hotter than red. It’s 7.5 times hotter than NIR. Why? Blue light absorbs strongly. Melanin and hemoglobin absorb it well.
Photobiomodulation Heating: Direct Comparisons and Real-World Evidence
Insights on heating from direct comparisons and real-world photobiomodulation tests: One study compared wavelengths directly. They looked at 980, 1064, 650, and 810 nm.
They aimed to find the most and least heating. 980 nm had the most heating. 1064 nm was less heating than 980. It was roughly equal to 650 nm red. But 810 nm had the least heating. This study used isolated tissue. Living tissue has thermoregulation. Our bodies send blood to cool the skin. Dead tissue lacks these mechanisms.
Andrew from GembaRed also did his own tests. I used high-intensity LED panels. Wavelengths were 630, 660, 810, and 850 nm. He measured temperature change on his“ arm. Red wavelengths (630, 660) caused the most heating. The 810 and 850 nm caused the least.
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What other factors affect your red light therapy? Many parameters influence results. Intensity is generally most important. Exposure time comes next in importance. Fluence follows as the third factor.
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Light Absorption and Penetration: How Wavelength Impacts Heat in Light Therapy
Why do we see differences in heat based on light absorption and penetration in light therapy? Photons must be absorbed to cause heat. Reflected light does not cause heat.
A recent study measured human skin reflection. For light skin, 60% reflects from 600-1120 nm. Higher reflection means lower heating.
For black skin, reflection varies. Red light (600-700 nm) reflects 10-30%. Melanin highly absorbs red light. So, red light causes more heat on darker skin. NIR (800-1120 nm) reflects 45-55% on black skin. This again confirms NIR is least heating.
Consider absorption characteristics. Below 600 nm, absorption is higher. Hemoglobin and melanin absorb more. This means more heat from red, yellow, green, and blue.
Longer infrared? Above 1120 nm, water absorption increases. This leads to more heating. You feel heat from far-infrared. You also feel it from NIR beyond 1120 nm. This is due to superficial water absorption.
Think about light penetration. NIR penetrates about twice as deep as red. This gives NIR more volume to disperse. The energy spreads out over a wider area. Our bodies can then thermoregulate better. Red light absorbs more superficially. This concentrates energy near the surface. That causes more dramatic heating.
High-Intensity Photobiomodulation: A Deeper Safety Consideration for Internal Tissues
There’s one important safety point for high-intensity photobiomodulation: internal tissues. High-intensity NIR reaches deeper tissues. Our brains and organs are sensitive to heat. Too much energy there can be problematic. Your skin is resilient to heat. But deeper tissues are not. Be mindful of total energy to sensitive areas.
Imagine two water tanks on a stove. The smaller tank heats fastest. More volume takes longer to heat. NIR is like the larger tank. It distributes energy over more tissue. Our bodies can cope with it better.
Optimizing Your Light Therapy Device: Practical Implications for Less Heat
How can you optimize your light therapy device to reduce heat output? Don’t ignore this important truth. If you want to avoid heat, prefer NIR wavelengths. The 800-900 nm and 1050-1120 nm ranges are best. They are the least heating wavelengths.
Feeling too much heat from your device? Reduce the red light intensity. Blue, green, and yellow also cause heat. If your device has them, reduce those too. Many people do the opposite. They might cut total intensity. But red light is often the main culprit.
