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The scientific studies of the last years showed that phototherapy with the UVB- rays of spectrum 311 nm, (nanometer - one billionth of a meter), possesses maximum therapeutic effectiveness with minimum erythema (abnormal reddening of skin) and can be compared to the effectiveness of the PUVA-therapy treatments.
UVB is thought sometimes even to be more effective than UVA, not only with psoriasis, but also with a number of other illnesses. UVB has been adapted for about 50 years. There is no need of applying Psoralene with UVB therapy, and it is safer, because it requires smaller radiation doses. The smaller volume of side effects can be also explained by the fact that UVB light does not penetrate deeper than the epidermis (outer layer of skin), and the keratolytic (peeling of the epidermis) processes proceed precisely in this layer of skin.
Narrow Band UVB (NB UVB) therapy - is a UVB phototherapy with the use of the rays of a narrow spectrum of the long-wave Ultraviolet light (with the peak of emission at the wavelength of 311 nm) is carried out 3-5 times a week from an initial dose of 0,1 J/cm2. In the absence of erythema (abnormal reddening of skin) the following procedure is increased by 0.1-0.2 J/cm2. The course of treatment consists usually of 20-30 procedures.
The photo-immunological effect of phototherapy is caused by the depth of penetration of the ultraviolet rays. UVB- rays act in essence on the epidermal keratinocytes (skin cell that make up 95% of the outer layer of the skin and synthesize keratin) and the Langerhans' cells (participate in the inflammatory response; release chemicals that mobilize immune system cells). Ultraviolet rays have an effect on the production of Cytokines, which possess immunosuppressive action, as well as they have an effect on the expression of molecules on the cellular surface and the induction of the cellular Apoptosis (programmed cell death), which, possibly, explains the therapeutic effect of the UVB.
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