By Dr Catherine Hamilton
Medical Practitioner | PBM Researcher
Updated May 2026
How does red light work?
Wavelengths in the red and near infrared light have two key properties:
Wavelengths in the red and near infrared light have two key properties:
They penetrate into the body - through skin, fat, muscle and even bone. With sufficient power, they can penetrate through the skull into the brain tissue.
They stimulate each and every kind of cell in the body. They are literally medicine at the cellular level.
The implications of these two properties are profound:
Red and near infrared light can directly affect cells, even those living several centimetres below the skin surface. This means that all the cells get an energy boost, thanks to the stimulation of the cell batteries, the mitochondria. For more about mitochondria, click here (the text is in the concertina section below).
Stimulating the mitochondrial battery means that all the cells suddenly get active. Very active. Here’s how.
When the mitochondrial proteins are given a dose of light, a series of chemical cascades are kick-started. These chemical cascades have three essential outcomes:
They make the cell active and able to do whatever it is supposed to do. This battery re-charge protects the cell and makes it function normally for a while. In the brain, the effect is called neuroprotection.
They stimulate the cell to begin the process of making new cells. This is absolutely brilliant, as new brain cells mean more action. This is called neurogenesis.
They change the chemical soup outside the cells, and this:
Makes the blood vessels sprout new branches. This is called angiogenesis, enabling more oxygen and glucose to be delivered to the cells.
Stops the inflammatory response, and the release of the kind of chemicals that cause pain and do damage to the tissue. Essentially the lights are giving all the tissue a potent anti-inflammatory treatment.
They strengthen the neural pathways by improving the ability of brain cells to work together. This is really important in pretty well everything we do and how we think.
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It is only in recent decades that we have discovered that many different health problems, especially neurodegenerative diseases, have one thing in common – failing mitochondria. It was an exciting moment when researchers realised that red and near infrared light could stimulate mitochondria and thus enable the cell to survive.
When a cell’s battery system is stimulated by red and near infrared light, the result is an improvement in brain function. It doesn’t matter what kind of cell, whether it is dedicated to producing dopamine, or deeply involved in managing sleep, memory, motivation, movement, mood, judgement, levels of anxiety and fatigue, light-stimulated mitochondria will kick it back into action.
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The direct effect is very powerful. Red and near infrared lights on the head result in happier functioning brain cells (neuroprotection), new brain cells being generated (neurogenesis), new blood vessels sprouting and bringing more oxygen to the cells (angiogenesis) and as well as acting to reduce inflammation.
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The indirect effect was first identified only recently. Red and near infrared lights shone on the lower part of the body can improve function in the brain. There are immune cells circulating in the bloodstream and they are able to pick up the light pulse and transport it to where it is most needed. For people with Parkinson’s disease, the cells in the basal ganglia are the main recipient.
An even more recent discovery is that mitochondria can pop in and out of cells, and travel to different parts of the body in the blood stream. They pick up light pulses and efficiently transport them to problem areas.
Exactly how the circulating immune cells and mitochondria know where to go is subject of much discussion. There must be sophisticated signalling systems at work. Just when we discover something new, a whole bunch of unknowns are revealed. So much to learn.