Psoriasis is a chronic inflammatory condition of the skin, where the patient has red plaques often topped with scales that are silver color. Psoriasis can be passed through genes or triggered by an abnormality in the immune system. Psoriasis can be treated with phototherapy, creams and ointments, tar mixtures, and various biologic treatments. Both men and women are affected by psoriasis, and it is often not visible in public as many people either try to hide the condition or are in treatment. At least 2% of the population has psoriasis. This differs per country. Psoriasis can affect the face, elbows, scalp, knees, and other areas as well. Psoriasis for a given individual may be a minor issue or could be severe, depending on the individual and severity of their condition.