When working with red-light therapy, joules are the most important measurement that we use to determine how much light emission creates the desired result. We are not talking about jewels like diamonds, jade and opal; although for anyone down the path of red light, we all know the sessions might be just as valuable! This measurement of energy is typically in milliwatts (mW) delivered per second; one joule is 1,000 milliwatts. The total energy measurement is joule per centimeter squared, (j/cm2.)
The goal of each light session is to create an effective dose on the focus area that saturates enough of the area to trigger a photobiomodulation response – the light energy stimulates and regenerates cells and tissues – without causing any adverse responses. Adverse responses could include overheating, tissue damage or a Herxheimer reaction, also known as a Jarisch-Herxheimer (JHR or herx) reaction of the body, which is like a toxin dump. Herx reactions can include a flu-like feeling or headache, and can occur if someone goes too fast and too soon into light therapy, or if the sessions are too frequent or intense. When you have achieved a desired dose, the ideal outcome from the session is called a Therapeutic Window.
Photobiomodulation (PBM) modulates the biological processes of the body with light energy (photons). The light energy given by devices is recharging our body’s processes so they can better perform their functions. Medically recognized benefits of PBM include alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regenerations.
When working with red-light therapy, joules are the most important measurement that we use to determine how much light emission creates the desired result.
For a therapeutic light session administered to boost circulation or reduce pain, I like to see an effective dose of 30-50 joules for PBM; for skincare, 5-15 joules will do the trick most of the time. Practitioners and light therapists agree that in one day, 100 joules should be the maximum amount a client receives combining all light therapy types. Duration truly depends on the person; but lower times with slower saturation typically yields better results. In the light world, faster and stronger is not always better, as your body needs time to process what the light energy is doing. I like giving 20-30-minute sessions, although “quick and strong” does sometimes have its place.
How do we know the total amount of joules a device is delivering per session? Ideally, the company you purchased your light therapy unit from has told you this or at least, has given you the power density (mw/cm2) of the device. If not, there are red-light meters on the market that will give you that reading. I highly encourage investing in one – to not only double-check that your device will do what it claims, but also to ensure it keeps up its light work!
A popular home and commercial red and infrared panel is labeled as 100 mW/cm2, but also states its power is up to 352W (352,000 mW). You can figure out the actual totals yourself. First, find the unit’s area – this panel is 182 centimeters tall and 44 centimeters wide – multiplying those together comes to an area of 8,008 cm2. The power density is the output per second divided by area, or 352,000/8,008. We can round to 43.95cm2 per second, which is far lower than what the label states. If this unit offers pulsed settings, you would divide that number in half or more, depending on the pulse frequency since the light energy is being reduced in bursts. Now, the formula to calculate the total dose in joules is power density x time = dose. This unit suggests ten-minute sessions at least 16 inches away from the body, and we will figure this out with 43.95×60 (seconds) = 2,637. Now, let us turn that into a total joules calculation – we will multiply by .001 (a milliwatt per second is .001 joule.) So, we take that 43.95 x .001 and determine that this particular device is emitting 0.04 joules per second. If our ideal goal is 30 joules, we divide 30/.04 and we end up needing 750 seconds, or 12.5 minutes total, assuming we are directly next to the light at its strongest. You lose about 50% of strength for each inch you are away from a light. I would like to meter this device to see what the output truly is and determine a proper dose time.
If a device was truly emitting 100mW/cm2, it would take five minutes of direct contact to reach a 30-joule session, ten minutes at an inch or so away, 15 minutes a little further away and so on. It is extremely important to know and understand the numbers you are working with and to ensure that the equipment you are using is truly emitting the light energy stated on the label.
Knowing that an appropriate dose of red light for skincare effects is up to 15 joules may help you create some skincare-based packages to offer at your wellness spa and salon. A huge hit at my salon is a Red-Light Facial paired with our Massage Chair session! A step up from this could be a Wellness Refresher that gives a 30-joule session, which is a good therapeutic dose in general. Then, knowing you should never exceed 100 joules in a day, if you offer different types of red-light services you now know to look out for that cap, or any negative side effects your client experienced, and can note in their files at what number of joules they had a negative reaction. On the positive side of offering high-quality light services, you can offer a Full-Body Booster with a higher number of joules for someone looking for the most light for their buck!
