Light therapy: how does it work and what does it treat?

November 15, 2020 6 mins read
Light therapy: how does it work and what does it treat?

Light up your life and improve your sleep by adding light therapy to your bedtime routine. For years, light therapy has been popular among beauty therapists, biohackers and athletes wanting to reduce inflammation and pain. But it has recently grown in popularity among those who want to improve their skin, lower inflammation, boost mitochondria production in their cells, live longer and sleep better.

Yes, light therapy can help improve the quality and duration of your sleep. Here’s how.

What is light therapy?

Light therapy is also referred to as photobiomodulation (PBM), phototherapy or photodynamic therapy. This type of treatment uses specific wavelengths of light to benefit your body in multiple ways, depending on the type of light used and the distance of the wavelengths.

Wavelength distance is measured in nanometers. Wavelengths between 630 to 670 nm and 810 to 880 nm are typically used in light therapy.

What is light therapy used to treat?

Depending on the type of light used, phototherapy is used to treat various conditions.

  • Red light: sleep disorders like insomnia, poor wound healing, inflammatory conditions like arthritis, jet lag and skin ageing
  • Blue light: bacteria on the skin, low energy and skin inflammation
  • Green light: migraines, hyperpigmentation, sunspots, inflammation, and under-eye circles
  • Sunlight: depression and anxiety, jet lag, Seasonal Affective Disorder (SAD) and sleep disorders like insomnia.

How does light therapy work for sleep?

When light hits photoreceptors in your eyes and in your skin, it can trigger different reactions in your body depending on the type of light.

Natural sunlight exposure has helped humans sleep better for thousands of years. Your body uses light to help it regulate your sleep-wake cycle, also referred to as your circadian rhythm, which signals to your body when to start preparing for sleep and when to wake up.

The sun emits a combination of visible light, ultraviolet light and infrared radiation. Visible light consists of seven colours, namely red, orange, yellow, green, blue, indigo, and violet. The colours of the sky change throughout the day because different coloured wavelengths scatter more easily than others. Blue light scatters more easily than red, for example. You get more blue light early in the day and more red light later in the day.

If you have an irregular sleep pattern, you can improve your sleep quality and symptoms of sleep disorders by mimicking natural light to recalibrate your body’s circadian rhythm. If you’re a shift worker, for example, you can use blue light to simulate the morning (time to wake up!) and red light to mimic sundown (time to sleep).

How effective is light therapy for sleep?

We are not saying you should expect miracles, but light therapy can make a big difference in the quality of your sleep, especially when paired with other ways to improve your sleep like avoiding caffeine six hours before bed, eating melatonin-rich foods and exercising during the day.

As with most things in life, light therapy has its benefits and disadvantages.

Benefits of light therapy for sleep

The benefits of phototherapy for sleep disorders depend on the type of light you use.

Red light

Red light can stimulate the production of melatonin, which can signal the body to start preparing for sleep. It can help reduce inflammation, as well as pain related to inflammation. It does this by helping to modulate inflammatory cytokines, which are signalling molecules that cause inflammation. It also helps speed up healing, so if your pain is coming from a recent injury or operation, or even a migraine, using light therapy can help you recover faster, so you will be able to sleep pain-free sooner.

Blue light

Blue light signals the start of the day. Exposure to blue light early in the morning can give you energy and help you sleep better at night. This is why going out and exposing your eyes and skin to the clear blue skies after waking up is a good idea.


Natural sunlight is not only crucial for regulating the circadian rhythm, but exposure also triggers vitamin D production in the body.

Vitamin D is vital to our health. A vitamin D deficiency can worsen symptoms of depression and anxiety, affect your sleep quality and cause symptoms of insomnia. It can lead to Seasonal Affective Disorder (SAD), which is a condition caused by a lack of sunlight. It commonly occurs in the Northern Hemisphere during winter when there is less sunlight exposure.

This is why people with mental health conditions and sleep disorders need to get plenty of sunlight and include vitamin D-rich foods in their diet, like egg yolks, fatty fish like salmon and mackerel, liver, cod liver oil and mushrooms.

You can also supplement with vitamin D (always choose vitamin D3), but sunlight exposure remains the best way to get more vitamin D.

Other benefits that are not related to sleep include:

  • Red light therapy boosts collagen production, which is essential for building connective tissue and will help keep your joints as healthy and young as possible. Collagen is crucial for maintaining a healthy skin structure. When collagen in your skin is broken down, wrinkles start to form. Red light therapy should be part of every anti-ageing routine.
  • Blue light therapy can improve your skin health by killing bacteria on the skin that can lead to acne and other infections.
  • Green light therapy improves the appearance of your skin as it can help reduce skin inflammation, hyperpigmentation and sunspots.
  • Sunlight exposure can help with weight management and bone health, and it can promote longevity.

Disadvantages of light therapy

Light therapy cannot be the only treatment approach for managing sleep disorders and improving sleep quality. It needs to form part of a holistic lifestyle approach. Additionally, it can be expensive to go for phototherapy treatments at an institute like a medical spa, or to buy your own light therapy device. Natural sunlight is the most affordable light therapy option for improving sleep quality and managing sleep disorders.

Side effects of light therapy

People who have conditions that affect the retina of the eye (like diabetes) should preferably avoid phototherapy, as too much light exposure can cause further damage.

Some of the side effects people can experience with light therapy include headaches, eye strain and irritability, but these are usually relatively mild and can be solved by changing the frequency, duration and intensity of the light therapy.

Using a specific light at the wrong time of day can also lead to side effects. While blue light exposure in the morning can promote sleep at night, doing it late in the day can do more harm than good. Blue light exposure increases energy and interferes with melatonin production, so you should not use a blue light therapy device later in the day.

Green light exposure before bed can also decrease melatonin production. Any green light and blue light emitted in the room from digital screens and LEDs should also be avoided. If you, your bed partner or your child need a night light, choose a red light instead. It is one of the best coloured lights for sleeping.

Ready to light up your sleep quality?

Strategic light exposure during the day can regulate your circadian rhythm, improve your mood and help improve symptoms of any sleep disorders you may have. It is non-invasive, doesn’t require that you take any medication, and is an excellent long-term strategy for good sleep.

Perhaps it is time to light up, so you can rest well when the lights are off.