A 311 nm lamp in a dermatology clinic, a red and near-infrared LED panel in a recovery room, and a bright-light box for seasonal depression all use light for different purposes. If you're comparing devices, start with the intended use. That determines which wavelengths, measurements, and safety documents matter.
What counts as phototherapy?
What phototherapy light actually is (and what it is not)
Phototherapy is the use of controlled light exposure for a specific therapeutic purpose. In a dermatology clinic, the term often refers to ultraviolet (UV) treatment. Product listings also use it for red and near-infrared light therapy and for bright-light boxes. In neonatal care, it usually refers to blue-green light for jaundice.
| Type | How the light is specified | Typical use or research area |
|---|---|---|
| Narrowband UVB (NB-UVB) | A narrow UVB band around 311 nm | Psoriasis and vitiligo [1] |
| Neonatal phototherapy | Blue-green light, approximately 460–490 nm | Newborn jaundice [2] |
| Bright-light therapy | Visible light, with illuminance given in lux | Winter-pattern seasonal affective disorder [3] |
| Photobiomodulation (PBM) | Red and/or near-infrared light, such as 660 nm and 850 nm | Studied for skin appearance and post-exercise recovery [7–9] |
How different types of phototherapy work
How phototherapy light works inside the body
Narrowband UVB acts mainly in the outer layers of the skin, where it can change local immune activity. Dermatology teams adjust exposure according to the treatment protocol and the patient's skin response. PUVA uses a separate approach. It combines UVA with psoralen, a drug that makes the skin more sensitive to UVA. [1]
Red and near-infrared PBM has been studied for its effects on cellular activity. One proposed pathway involves cytochrome c oxidase, a mitochondrial enzyme involved in cellular energy production. Experiments in intact cells and experiments with the isolated enzyme have produced different findings. A proposed mechanism on its own gives little information about what a specific device will do in a clinical setting. [4, 5]
Bright-light therapy works through light-sensitive cells in the retina that help set the body's internal clock. Both the timing and the brightness of the exposure matter. The National Institute of Mental Health describes a UV-filtered 10,000-lux light box for winter-pattern seasonal affective disorder. [3, 6]
Where phototherapy is used
The main uses of phototherapy light across health settings
Dermatology. Clinicians may use narrowband UVB for psoriasis or vitiligo when topical treatment is unsuitable or has provided insufficient relief. It is also an option for some patients with atopic eczema. The choice depends on the condition and the patient's treatment history. [1]
Newborn jaundice. Blue-green light changes bilirubin into forms the body can eliminate more readily. The clinical team decides when to start treatment using the baby's bilirubin level, age, and risk factors. The American Academy of Pediatrics describes approximately 460–490 nm as the preferred wavelength range for these devices. [2]
Post-exercise recovery. One randomized study applied 660 nm and 850 nm LEDs at specific points on the legs before running sessions. A separate placebo-controlled study used those wavelengths after repeated sprints and found similar recovery outcomes with active and sham exposure. If you see either study cited for a full-body panel, check the timing, placement, and dose in the actual protocol. [7, 8]
Skin care. A split-face trial evaluated 633 nm and 830 nm LEDs for changes in wrinkles and skin elasticity. Acne is a separate question. The American Academy of Dermatology found the evidence too limited to make a general recommendation for laser and light-based acne procedures in its updated guideline. [9, 10]
How to compare irradiance across panels
Why "same wavelength" does not mean same result — the measurement problem most buyers miss
Ask where the reading was taken
Irradiance is the optical power arriving per unit area at the measurement surface. For red light therapy panels, it is usually reported in mW/cm². A center reading samples the point directly in front of the panel's center. To assess coverage, ask for a grid of readings at the intended distance, along with the average, minimum, and area measured. [11]
At the same distance, a 30° lens typically gives a narrower beam footprint than a 60° lens. The beams from individual LEDs overlap, so the irradiance map of the finished panel shows how much light reaches the edges. At close range, a large panel can depart from the inverse-square behavior of a point source. Take readings at each distance you intend to use. [12]
An integrating sphere can measure the total radiant flux emitted by an LED. To find the irradiance delivered by a finished panel at a stated distance, use a calibrated detector at that measurement plane. For a fair comparison, check that the reports specify where the distance was measured from, which detector and operating mode were used, and what area was sampled. Six inches is 15.24 cm. A center reading at one of those distances and a grid average at the other still describe different measurements. [13]
Read irradiance and exposure together
Radiant exposure is the total light energy arriving per unit area over a given time. Multiply irradiance in mW/cm² by time in seconds, then divide by 1,000 to get J/cm². For pulsed output, use the average irradiance over the exposure. In a bench test, an average of 20 mW/cm² over 300 seconds gives 6 J/cm² at the detector. [11]
Match the paperwork to the device
For a wholesale order, request optical measurements from more than one finished unit if you need to verify batch consistency. Check that the test report lists the same model and configuration you're buying.
ISO 13485 covers a medical-device quality management system. For a CE-marked product, review the EU Declaration of Conformity and the legislation it cites. FCC documentation addresses applicable radio-frequency requirements, and an ETL listing identifies the safety standards the product was tested against. In the United States, FDA establishment registration and device listing are separate from FDA clearance or approval. Check the documents for the specific model and destination market. [14–18]
Side effects and when to seek medical advice
Risks, side effects, and when to seek medical guidance
UV phototherapy. Redness is the most common short-term effect of narrowband UVB. More severe reactions can include blistering. Long-term skin cancer risk is well established for PUVA, while the evidence for narrowband UVB is less clear. Tell the treatment team about any new medicines and report painful redness or blistering. Some patients can receive prescribed narrowband UVB at home through a supervised program. [1]
Red and near-infrared light. Temporary irritation can occur. Follow the instructions for distance, session length, and eye protection. For a clinic or commercial installation, check which exposure conditions the optical safety report covers. IEC 62471 provides a framework for evaluating optical radiation hazards from lamps and lamp systems, including LEDs. [19, 20]
Bright-light therapy. Ask a clinician about the setup if you have an eye condition or take medication that increases sensitivity to light. A clinician can advise whether supervision or another treatment is appropriate. [3]
What to check before choosing a device
Key Takeaways
If you're choosing a full-body panel for a recovery room, measure the space between the panel and where users will sit or stand. Ask each supplier for an irradiance map at that distance and over the area you need to cover. For a clinical application, start by checking whether the device and protocol match the evidence for the intended use.
FAQ
What is phototherapy light used for?
Clinical uses include narrowband UVB for psoriasis and vitiligo, blue-green light for newborn jaundice, and bright light for winter-pattern seasonal affective disorder. Researchers have also tested red and near-infrared PBM for outcomes such as skin appearance and post-exercise recovery. [1–3, 7–9]
What are the side effects of phototherapy?
They depend on the light source and dose. Narrowband UVB can cause redness or burns, and red light therapy can cause temporary skin irritation. Follow the instructions for the specific device and tell the treatment team about photosensitizing medicines. [1, 19]
Is UV phototherapy safe?
Narrowband UVB is an established treatment. A prescribed schedule lets the care team adjust the dose and monitor reactions. The risks differ by UV modality, and repeated PUVA exposure carries a documented increase in skin cancer risk. [1]
What's the difference between light therapy and phototherapy?
The terms overlap. A dermatologist may use "phototherapy" to mean UV treatment, while "light therapy" on a product page can mean a red LED panel or a bright-light box. Look for the full name of the modality and the use described in the device instructions. [1, 3, 19]
About the author
REDDOT LED is a Shenzhen-based manufacturer of red and near-infrared light therapy devices, founded in 2010. The company provides OEM and ODM services for brands and distributors. About REDDOT LED · Product and market compliance documents
Related guides
Related Guides
- Learn what detector choice, test distance, and a grid of readings tell you about panel output. How to measure irradiance
- Work through the conversion from mW/cm² and seconds to J/cm². How to calculate radiant exposure
References
- Goulden V et al. British Association of Dermatologists and British Photodermatology Group guidelines for narrowband UVB phototherapy (2022). Full guideline
- American Academy of Pediatrics. Technical report on phototherapy for neonatal hyperbilirubinemia in infants born at 35 or more weeks of gestation (2024). PubMed · Full report
- National Institute of Mental Health. Seasonal affective disorder and bright-light therapy. NIMH guidance
- Wong-Riley MTT et al. Photobiomodulation and cytochrome c oxidase in cultured primary neurons (2005). PubMed
- Quirk BJ and Whelan HT. Red and near-infrared light in an isolated cytochrome c oxidase experiment (2016). PubMed
- Berson DM et al. Phototransduction by retinal ganglion cells that set the circadian clock (2002). PubMed
- Randomized trial of 660 nm and 850 nm LED PBM during endurance running training (2019). PubMed
- Malta ES et al. Placebo-controlled study of LED PBM after sprint interval training (2019). Full study
- Lee SY et al. Randomized split-face study of LED phototherapy for skin rejuvenation (2007). PubMed
- American Academy of Dermatology. Updated acne management guideline and evidence for light-based procedures (2024). Guideline summary
- International Commission on Illumination (CIE). International Lighting Vocabulary. Irradiance · Radiant exposure
- CIE. The distance law and its point-source assumption. International Lighting Vocabulary
- National Institute of Standards and Technology (NIST). Optical measurements for total LED output and for irradiance at a reference plane. Total radiant flux · Spectral irradiance calibration
- International Organization for Standardization. ISO 13485:2016 requirements for medical-device quality management systems. ISO standard overview
- European Commission. CE marking, conformity assessment, and the EU Declaration of Conformity. CE marking guidance
- U.S. Federal Communications Commission. Radio-frequency equipment authorization procedures under 47 CFR Part 2, Subpart J. Electronic Code of Federal Regulations
- Intertek. The ETL Listed Mark and applicable North American safety standards. ETL listing overview
- U.S. Food and Drug Administration. Medical-device registration, listing, clearance, and approval. FDA guidance
- American Academy of Dermatology. Red light therapy, possible side effects, and home-device safety. AAD guidance
- International Electrotechnical Commission. IEC 62471 on the photobiological safety of lamps and lamp systems. IEC standard overview