Phototherapy refers to medically therapeutic exposure to light, or using light to treat medical problem. Ultraviolet (UV) light is most frequently used, and it is broken down into three band-ranges. the A range (the "colors" that generate suntans; ~320-400 nm), the B range (the "colors" that can cause sunburns; ~290-320 nm), and the C range (the "colors" that are lethal to most living things; ~100-250 nm); these bands are also known as UVA, UVB and UVC.
While UVC lights are used in a variety of air & water purification and sterilization systems, there are currently no therapeutic uses for UVC light; it is simply too intense.
UVA lamps are most commonly used in tanning systems, but they are also used medicinally for what’s called "PUVA" therapy. For decades, PUVA was the only effective treatment for many people.
Too much UVB light and you’ll quickly get a sunburn, but when carefully administered it can be the solution for millions of people suffering with psoriasis, along with a long list of other conditions.
Within the UVB range, there is a very specific frequency range that appears to be what most skin problems are thirsty for; this is called "Narrowband UVB" (nbUVB; 311-313 nm) and it is effective for roughly 80% of all applicable patients. Its only side effects are sunburns (if you over-do it) and cataracts (if you don’t shield your eyes). While a history of moderate to severe sunburns has been linked to an increased risk for certain skin cancers, the proper use of UVB light has never been shown to increase the risk for skin cancer; and that’s with almost a century of medical use.
Phototherapy, specifically nbUVB, is most often used to treat conditions like psoriasis, vitiligo and eczema. Less common problems that respond well to nbUVB are certain types of dermatitis, prurigo, porphyria, pruritis, a form of cancer usually called CTCL (Cutaneous T-Cell Lymphoma). And phototherapy is safe enough to be used with pregnant women and children.
The basic goal behind nbUVB therapy is determining how much light exposure causes your skin to burn by slowly increasing your exposure amounts untill your skin begins to burn. You take treatments that are just below that amount every other day (at most) until you are clear again following the basic protocol developed by the National Psoriasis Foundation.
