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UV-B lamps are lamps that emit a spectrum of ultraviolet light with wavelengths ranging from 290-320 nanometers. This spectrum is also commonly called the biological spectrum due to the human body's sensitivity to light of such a wavelength. UV-B light does not tan the skin very much, compared to the UV-A lamps that are used in tanning beds.
Types of UV-B lamps
UVB spectrum is 290-320 nanometer (280-320 in Europe).
There are two types of UV-B lamps: broad-band (also called wide-band, or just "UVB") and newer type called "narrow-band".
Broad-band lamps produce radiation over the full UVB spectrum of 290-320 nanometer wavelength, with a peak wavelength of 306 nanometer.
Narrow-band lamps produce radiation of 311-313 nanometer wavelength, with a peak wavelength of 312 nanometer. Because of the narrow spectrum of 2 nanometer (311-313) they are called narrow band.
Some of the power of the Broad-band UV-B lamps is below 300 nanometer.
The Narrow Band lamps give only from 311 to 313 nanometer, and not below 300 nanometer.
Narrowband lamps require 20 times higher dose to cause treat skin diseases, and this high dose is considered to be not healthy.
Broadband lamps give some energy under 300 nanometer, that is considered not healthy.
There is an argument what is more unhealthy: The high dose of the narrowband light, or the below 300 nanometer of the broadband lamps.
The Broadband UVB lamps requires short exposure time of about 1 minute (0.15 Joule) and without paying attention to the time there is higher chance to burn the skin, while with the narrowband it is rare, because the time can be 20 minutes (3 joule). Strong redness of the skin from overexposure is painful and it can cause skin cancer.
Treating full body Psoriasis (Psoriasis Vulgaris) requires about 20 bulbs of 100 watt with average exposure time of 10 minutes, while with broadband 4 bulb of 100 watt will require only 2 minutes.
Phototherapy clinics can afford expensive and big exposure units, and they can use narrowband.
For private use, if the person cannot buy a big and expensive unit with 20 bulbs of 100 watt, he can get a unit with 4 bulbs of 100 watt, and the result will be about the same, and the exposure time will be only 2 minutes.
Treating skin diseases
There are thousands of dermatology clinics around the world that treat skin ailments with UV-B lamps. Many people who suffer from psoriasis or other skin diseases have their own UV-B lamp for home treatment. A small lamp is used to treat limited areas of the skin, while full body cabins are available in clinics and hospitals.
Overexposure to UV-B light can burn the skin, so the exposure time must be regulated by a timer that turns off the lamp.
Increasing vitamin D3
When the skin is exposed to UV-B light, cholesterol in the skin is transformed into vitamin D3. In general the skin does not need much UV-B energy to generate vitamin D3, and 15 minutes of strong sunshine every day is usually considered enough.
In Northern European countries especially in the winter when sunlight is scarce, pregnant women may receive UVB light in clinics to assure that their babies have an adequate amount of vitamin D3 when born.
Animals need UV-B light to produce vitamin D3 and strong bones. Zoos have UV-B lamps for reptiles kept indoors. Reptile keepers in a home environment can purchase UV-B/UVA emitting bulbs from pet stores to provide their reptiles with the required amount of UVB/UVA they need to generate vitamin D3. Such lights are branded Creature World or Repti Glo and used for a period of 10–12 hours per day to give the required exposure. These lamps simulate the sun spectrum and thus produce mostly visible light and a very small amount of UV-B light, like the sun.
UV-B treatments for treating skin diseases (psoriasis, vitiligo, atopic dematitis, etc.) are given in a very low dosage. The treatments take only few minutes.
The maximum dose of broadband UV-B is 0.5 Joules per treatment. The maximum dose for narrowband UV-B is 3 Joules per treatment. This low dosage does not increase the risk of skin cancer and UV-B phototherapy remains a very safe treatment. Research citing ten year of experience of phototherapy in Yonsei Medical Center has not revealed any cases of malignancy in the skin.
Too much UV ultraviolet radiation of an undesirable wavelength may lead to direct DNA damage, sunburn, and skin cancer. In contrast to exposure to UV-B light given at low dosage, it was found that UV-A light increases the risk of skin cancer because of the problematic wavelength and because it is given in a much higher dosage.
Because PUVA treatments (UV-A + Psoralen) and tanning beds (UV-A only) supply longer wavelength radiation, and are also given in higher dosage of 10-100 Joules, the UV-A light penetrates the skin and reaches the dermis, which can cause DNA damage.
- http://www.iarc.fr/en/publications/pdfs-online/wrk/wrk1/ArtificialUVRad&Skin4.pdf[full citation needed]
- Lee, Ernest; Koo, John; Berger, Tim (2005). "UVB phototherapy and skin cancer risk: A review of the literature". International Journal of Dermatology 44 (5): 355–60. doi:10.1111/j.1365-4632.2004.02186.x. PMID 15869531.
- Park, Sang Hoon; Hann, Seung Kyung; Park, Yoon Kee (1996). "Ten-year experience of phototherapy in Yonsei Medical Center". Yonsei Medical Journal 37 (6): 392–6. doi:10.3349/ymj.19184.108.40.2062. PMID 9048491.
- Matsumura, Yasuhiro; Ananthaswamy, Honnavara N (2004). "Toxic effects of ultraviolet radiation on the skin". Toxicology and Applied Pharmacology 195 (3): 298–308. doi:10.1016/j.taap.2003.08.019. PMID 15020192.