“Psoriasis is a long-lasting autoimmune disease characterized by patches of abnormal skin. These skin patches are typically red, dry, itchy, and scaly. On people with darker skin the patches may be purple in colour. Psoriasis varies in severity from small, localized patches to complete body coverage.”
Psoriasis outbreaks have been frequently associated with lifestyle, viral infections, bacterial infections, medications and genetic factors - but no exact mechanism of action is known.
Also see : Eczema