When is too much, too much?


LED Light Therapy: The Facts About Power Intensity

Thanks to thousands of clinical trials and studies, most all researchers agree that photobiomodulation (PBM) therapy or LED Light Therapy is beneficial — and shows a great deal of promise — in treating a myriad of diseases and conditions, both physical and psychological.

With this widely accepted scientific premise established, many questions remain as to what precise power intensities and dosages provide the most benefit for each individual disease and condition. A great deal of study is being dedicated to answering this question, and it will likely be years, if not longer, before we have an all-encompassing understanding of Light Therapy’s absolutely remarkable potential.


  • Power Intensity: milliwatts per centimeter-squared (mW/cm2)
  • Irradiance: milliwatts per centimeter-squared (mW/cm2)
  • Dosage: Joules per centimeter-squared (J/cm2)
  • Milliwatt (mW): one thousandth of a watt (W)
  • Joule (J): a derived unit of energy established by the International System of Units


Higher Intensity Doesn’t Equal Better Treatment

All the research surrounding Light Therapy has made one fact clear — when it comes to power intensity, more does not equal better.


It stands to reason, doesn’t it? The human body is designed to absorb only a certain amount of photons at a certain rate. Bombarding it with higher intensities does nothing, and in many cases, it can even be detrimental.

As with all things, moderation is the key. It’s like eating — you can’t eat three days’ worth of food in one sitting and expect to be full for the subsequent 72 hours. The body just doesn’t work that way.

Smaller quantities of food ingested over time is the only sustainable approach to providing your body with the nutrition it needs to function. And so it is with Light Therapy. Treatment that uses the correct dosages and intensities, delivered over time, is the best approach to optimal healing.


Biphasic Dose Response

How have researchers arrived at this conclusion? By looking at Biphasic Dose Response. This is when the body has two distinct responses to a stimulus based on concentration. The concept is derived from the Arndt-Schulz rule (Wikipedia contributors, 2021), which states that every stimulus either stimulates, inhibits, or terminates — it all depends on the concentration of that stimulus.

So, by comparing two dosages/power intensities, each delivered over specific durations, we can measure which Light Therapy treatments either benefit the body, have little or no effect on the body, or harm the body.

Just like food. Which one has the greatest benefit — eating three meals in a single sitting or eating three meals over three sittings? It’s all about how much you receive over how much time.


Power Intensity Review

This wonderful 2011 review (Huang et al., 2011) provides some great examples. For instance, one study measured oral mucositis in hamster models, using red light therapy. The models received two different irradiances:

  • 55 mW/cm2 for 16 seconds per point
  • 155 mW/cm2 for 6 seconds per point

The models that received the lower power intensity for a longer period showed reduced severity of mucositis, while the models that received the higher intensity for a shorter duration showed no significant differences compared to controls.

Another study in the same review measured wound tensile strength in rat models, using red light at a dosage of 5J/cm2. A power intensity of 4mW/cm2 for 1,250 seconds showed positive results. But 15 mW/cm2 for 333 seconds showed no positive results.

To review the Visum Light Dosing Table, please click here.


The Takeaway

We’ve heard it a thousand times, and it holds true in all aspects of life: more does not equal better. When it comes to your Light Therapy, whether delivered at a clinic or in the comfort of your own home, practice patience. Small, consistent treatments over time are the key to receiving all the healing benefits Light Therapy has to offer.

Want to see why the patent-pending Visum Light is one of the most versatile handheld light therapy devices on the market, ideal for proper dosing and power intensity settings? Take a look here.

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Huang, Y.-Y., Sharma, S. K., Carroll, J., & Hamblin, M. R. (2011). Biphasic dose response in low level light therapy – an update. Dose-Response: A Publication of International Hormesis Society, 9(4), 602–618. https://doi.org/10.2203/dose-response.11-009.Hamblin

Wikipedia contributors. (2021, October 23). Arndt–Schulz rule. Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/w/index.php?title=Arndt%E2%80%93Schulz_rule&oldid=1051428222

Wikipedia contributors. (2022, May 29). International System of Units. Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/w/index.php?title=International_System_of_Units&oldid=1090489006