What is psoriasis? What causes psoriasis? Is there a cure or treatment for psoriasis? Psoriasis is a skin condition, it is a disease, but it is not contagious. The name comes from the Greek word for "itch." It can be hereditary, caused by external influences (allergic reaction to foods or the environment) and sometimes stress. 4-5% of the population is known to be affected, and this number is growing. However, it is suspected that 1 in 5 people have some form of psoriasis either descripts or none descript.