/content/imprint/oecd. 1  Browse by Theme Agriculture and Food. Development. 2  Browse by Country A-C. D-I. 3  Browse by Theme & Country Select one or more items in one or both lists to browse for the relevant content. Theme Select / Clear all.  Catalogue BOOKS. PAPERS.
A variety of factors -- ranging from emotional stress and trauma to streptococcal infection -- can cause an episode of psoriasis. Recent research indicates that some abnormality in the immune system is the key cause of psoriasis.
Psoriasis causes patches of thick red skin and silvery scales. Patches are typically found on the elbows, knees, scalp, lower back, face, palms, and soles of feet, but can affect other places (fingernails, toenails, and mouth). The most common type of psoriasis is called plaque psoriasis.