Psoriasis is a common chronic skin disease, which is quite difficult to cure. Its typically frequent recurrences deeply affect mental health of the patients causing shame and embarrassment and a compromised lifestyle. Psoriasis affects about 0.1% - 2.84% in the world population, with higher percentage in Europe and America. It is 13% in America, 1.6% in United Kingdom, 2.84 in Denmark, and it is as high as 11.8% among the Kazakhs in the Polar Regions of the USSR. Psoriasis is rarely Caucasian, less so in the yellow races and rarely among the Negroes. American Indians and Fijians are free from this disease.

Investigations in to the Etiology of psoriasis have been carried out extensively all over the world, but the real cause of the disease is not as yet completely known. So far as we understand, the onset of psoriasis is associated with heredity, infections, mental disturbances. Clinical studies proved that the families of about 30% of psoriasis patients have history of the disease. Psoriasis can be caused by viral and streptococcus infections, such as the common cold and tonsillitis, which often lead to an attack or exacerbation of the disease. Psychic trauma and emotional stress can also lead to an attack or exacerbation.