Psoriasis vulgaris is a hereditary disease with a multi-factorialgenesis, appearing in 1-3% of the European population (Lampi , 198 3). Typical changes in the skin include hyperkeratosis, parakeratosis and akantosis. They are attributed to an increased mitosis rate in the basal regions of the epidermis and disorders of the maturing and differentiation of keratinocyres. These farreaching and infectious changes of dermis and epidermis cause the typical desquamation of the stratum corneum. Mechanic-, infectious- and psychosomatic factors are adequately researched as triggers of Psoriasis vulgaris. Nonetheless, the ethiology and pathogenesis of psoriasis are for the most part unexplored (Jung,1995).
To this day, there is only a symptomatic treatment with the aim of alleviating or, if possible, eliminating the skin manifestation. A secondary aim is to keep the patient relapse-free as long as possible. Numerous therapeutic substances exist , some being very fast-acting, but their applications often strain the patient, demand a high compliance and in some cases can be classified as risky (Braun-Falco 1987). These include keratolysis with salicylic acid- or urea ointments, especially anti-psoriatric local therapy using dithranol, calcipotriol, tar ointments or steroids and systemic treatments with retinoids and steroids. The same is true for ultraviolet-phoro-therapy (SOP) and the phorochemo-therapy after the application of 8-Methoxypsoralen(PUVA). According to present knowledge, none of the therapeutic methods named above offer a safe and practicable long-term therapy.
A topical long-term treatment is for the most part unavoidable, since most psoriasis patients have to deal with their disease all life long. Therefore, it seems reasonable to look for new treatment strategies that would reduce the amount of risky medication.