Understanding Narrowband UVB Phototherapy

The treatment of choice for psoriasis, vitiligo, and eczema

Narrowband UVB Phototherapy – The Basics

“Narrowband” UVB has become the phototherapy t because it delivers the largest amounts of the most beneficial wavelengths of UV light, while minimizing the potentially harmful wavelengths. 

Conventional “Broadband” UVB lamps emit light in a broad range over the UVB spectrum, including both the therapeutic wavelengths specific to the treatment of skin diseases, plus the shorter wavelengths responsible for sunburning (erythema). Sunburning has a negative therapeutic benefit, increases the risk of skin cancer, causes patient discomfort, and limits the amount of therapeutic UVB that can be taken.  

“Narrowband” UVB lamps, on the other hand, emit light over a very short range of wavelengths concentrated in the therapeutic range and minimally in the sunburning range, exploiting a “sweet spot” between the two around 311 nm. UVB-Narrowband is therefore theoretically safer and more effective than UVB-Broadband, but requires either longer treatment times or equipment with more bulbs to achieve maximum dose, which is upon slight onset of mild skin reddening after treatment, known as “sub-erythema”. Solarc’s UVB-Narrowband models have a “UVB-NB” suffix in the model number, such as 1780UVB‑NB. Solarc’s UVB-Broadband models have only a “UVB” suffix, such as 1740UVB. “Narrowband UVB” was developed by Philips Lighting of Holland and is also known as: Narrow Band UVB, UVB Narrowband, UVB‑NB, NB‑UVB, TL/01, TL‑01, TL01, 311 nm, etc., (where “01” is the Philips phosphor code embedded in UVB-Narrowband bulb part numbers).

And for a more detailed explanation: 

Understanding Narrowband UVB Phototherapy

“Narrowband” UVB (UVB-NB) has become the phototherapy treatment of choice for psoriasis, vitiligo, atopic dermatitis (eczema), and other photoresponsive skin disorders. Understanding the benefits of “Narrowband” UVB versus conventional “Broadband” UVB phototherapy requires an understanding of light and the processes it affects.

The spectrum of optical radiation (light) is made up of different wavelengths of “light” ranging from 100 nanometers (nm) in the ultraviolet (UV) range to 1 millimeter (mm) in the infrared (IR) range. Visible light spans from about 380 nm (violet) to 780 nm (red) and are known as the “colors” that we see with our eyes. Ultraviolet is invisible and ranges from 380 nm down to 100 nm, and is further subdivided into UVA (315-380 nm), UVB (280-315 nm), and UVC (100-280 nm).

FIGURE A shows the relative intensities of natural “light” reaching the earth’s surface after filtering by the earth’s atmosphere. Humans have evolved being exposed to all these wavelengths, so our skin has developed responses to use the light beneficially (Vitamin D) and to protect us from over-exposure (hereditary skin pigmentation and tanning). “UVB Narrowband” is highlighted at 311 nm and occurs naturally in sunlight, but not in great amounts. The earth’s atmosphere filters out nearly all light less than about 300 nm.
understanding narrowband uvb phototherapy
narrawband uvb phototherapy

Different wavelengths of “light” produce different effects on materials. Many important processes have been scientifically studied to determine the relative contribution of each wavelength to the studied process. Graphs known as “action spectrum” are used to describe these relationships. The greater the “action spectrum sensitivity”, the more responsive the process to that wavelength.

The action spectrum for psoriasis has been studied1,2 to determine that the most therapeutic wavelengths are 296 to 313 nm. As shown in FIGURE B, conventional UVB-Broadband lamps cover this range and have been used successfully for more than 60 years.

The action spectrum for “sunburning” of human skin, also known as “erythema”, has also been studied.11 Erythema is dominated by the lower wavelengths (less than 300 nm) of the UVB range. Unfortunately, conventional UVB-Broadband lamps produce a large amount of “light” in this erythemogenic range. These wavelengths produce burning and have less therapeutic value. What’s more, the onset of burning limits the UVB dose3 and erythema is a risk factor for skin cancer. Erythema also causes patient discomfort, which may discourage some patients from taking treatments. The grey shaded area in FIGURE C gives a graphical representation of the substantial erythemogenic content of UVB-Broadband.

uvbbroadband erythema understanding narrowband uvb phototherapy

"So why not develop a light source that produces most of its output in the psoriasis action spectrum and minimizes light in the erythema action spectrum?"

uvbnarrowband erythema understanding narrowband uvb phototherapy

In the late 1980’s, Philips Lighting of Holland developed just such a lamp, known as the “TL-01” or “UVB Narrowband” lamp. The smaller grey shaded area in FIGURE D shows that UVB-Narrowband lamps have considerably less erythemogenic output (sunburning potential) than conventional UVB-Broadband lamps. This means that more therapeutic UVB can be delivered before erythema occurs, and since erythema is a risk factor for skin cancer, these new lamps should theoretically be less carcinogenic for the same therapeutic results4,5,6,7. Furthermore, and critical to the success witnessed by home UVB-Narrowband phototherapy, it becomes much more possible that the disease is controlled without ever reaching the erythemogenic threshold9,10, which was always a problem with UVB-Broadband treatments. It is interesting to note that the peak of the UVB-Narrowband curve is about ten times higher than the UVB-Broadband curve, thus the source of the name “Narrowband”.

More recent studies have confirmed these findings and also determined that UVB-Narrowband has fewer burning incidents and longer remission periods than UVB-Broadband. When compared to PUVA (Psoralen + UVA-1 light), UVB-Narrowband has significantly fewer side effects and has replaced it in many cases8.

One disadvantage of UVB-Narrowband is that, because the maximum dosage is limited by the onset of slight erythema, and UVB-Narrowband is less erythemogenic than UVB-Broadband, longer treatment times are required. This can be compensated by increasing the number of bulbs in the device4,5,6,7. For instance, based on Solarc’s home phototherapy after sales follow-ups for UVB-Broadband, the 4-bulb 1740UVB provides reasonable treatment times; whereas for UVB-Narrowband, the 8-bulb 1780UVB-NB is a common choice. The theoretical ratio of erythemogenic potential of UVB-Broadband to UVB-Narrowband is in the range of 4:1 to 5:1.

Other diseases such as vitiligo, eczema, mycosis fungoides (CTCL), and many others have also been successfully treated with UVB-Narrowband, generally for the same reasons as described above for psoriasis.

Another interesting benefit of UVB-Narrowband is that it is likely the best fluorescent lamp type for making Vitamin D (FIGURE E) in human skin, for use instead of natural sunlight (which includes harmful UVA), or for those that cannot absorb adequate oral Vitamin D (tablets) due to problems in the gut. The subject of Vitamin D has received tremendous media attention lately, and for good reason. Vitamin D is essential to human health, yet many people are deficient, especially those who live at higher latitudes, far away from the earth’s equator. There is increasing evidence that Vitamin D protects against the development of many chronic diseases, including cancer (breast, colorectal, prostate), cardiovascular disease, multiple sclerosis, osteomalacia, osteoporosis, type 1 diabetes mellitus, rheumatoid arthritis, hypertension, and depression. For much more information, please visit these webpages: Vitamin D Phototherapy FAQ & Lamps for Vitamin D.

uvbnarrowband vitamind understanding narrowband uvb phototherapy

The prevailing opinion in the dermatology community is that UVB-Narrowband will eventually replace UVB-Broadband as a treatment option, especially for home phototherapy. This is clearly supported by Solarc Systems’ trend in home phototherapy equipment sales, with the sales of UVB-NB devices now outpacing UVB‑BB sales by about 100:1. Solarc’s UVB-Narrowband models have a “UVB‑NB” suffix in the model number, such as 1780UVB‑NB. Solarc’s UVB-Broadband models have only a “UVB” suffix, such as 1740UVB.

Solarc Systems would like to thank the good people at Philips Lighting for developing the UVB-Narrowband product line, and helping so many of us worldwide manage our skin problems safely and effectively. Note: The figures used in this document are simplified representations. The UVB-Broadband curve is derived from the Solarc/SolRx 1740UVB and the UVB-Narrowband curve is derived from the Solarc/SolRx 1760UVB‑NB.

We encourage you to research this important topic further.


1 PARRISH JA, JAENICKE KF (1981) Action Spectrum for phototherapy of psoriasis. J Invest Dermatol. 76 359
2 FISCHER T, ALSINS J, BERNE B (1984) Ultraviolet-action spectrum and evaluation of ultraviolet lamps for psoriasis healing. Int. J. Dermatol. 23 633
3 BOER I, SCHOTHORST AA, SUURMOND D (1980) UVB phototherapy of psoriasis. Dermatologica 161 250
4 VAN WEELDEN H, BAART DE LA FAILLE H, YOUNG E, VAN DER LEUN JC, (1988) A new development in UVB phototherapy of psoriasis. British Journal of Dermatology 119
5 KARVONEN J, KOKKONEN E, RUOTSALAINEN E (1989) 311nm UVB lamps in the treatment of psoriasis with the Ingram regimen. Acta Derm Venereol (Stockh) 69
6 JOHNSON B, GREEN C, LAKSHMIPATHI T, FERGUSON J (1988) Ultraviolet radiation phototherapy for psoriasis. The use of a new narrow band UVB fluorescent lamp. Proc. 2nd Eur. Photobiol. Congr., Padua, Italy
7 GREEN C, FERGUSON J, LAKSHMIPATHI T, JOHNSON B 311 UV phototherapy – An effective treatment for psoriasis. Department of Dermatology, University of Dundee
HEMPER M, HONIGSMANN H (1999) Narrowband UV-B phototherapy vs photochemotherapy in the treatment of plaque-type psoriasis. Arch Dermatol 1999;135:519-524
9 WALTERS I, (1999) Suberythematogenic narrow-band UVB is markedly more effective than conventional UVB in treatment of psoriasis vulgaris. J Am Acad Dermatol 1999;40:893-900
10 HAYKAL K-A, DESGROSEILLIERS J-P (2006) Are Narrow-band Ultraviolet B Home Units a Viable Option for Continuous or Maintenance Therapy of Photoresponsive Skin Diseases? Journal of Cutaneous Medicine & Surgery, Volume 10, Issue 5 : 234-240
11 Erythema reference action spectrum and standard erythema dose ISO-17166:1999(E) | CIE S 007/E-1998
12 Action Spectrum for the Production of Previtamin D3 in Human Skin  CIE 174:2006