Psoriasis is a chronic, noncontagious skin condition
characterized by scaling and inflammation. The inflamed skin
forms red, thickened areas with silvery scales. The condition is
most commonly found on the scalp, elbows, forearms, knees,
shins, ankles, and lower back. The inflammation may also affect
the fingernails, toenails, soft tissues of the mouth, genitalia,
and joints. The inflamed skin is usually asymptomatic, but may
cause pain and discomfort by cracking. Psoriasis is rarely
itchy. The exact cause of psoriasis has not been determined, but
current theories suggest that it may be a disorder of the immune
system. It appears that T-cells, a type of white blood cell that
normally protects the body against infection and disease,
trigger inflammation and excessive skin cell reproduction, which
causes skin to shed too rapidly. Psoriasis is also believed to
be associated with other cellular, biochemical, and metabolic
defects. Psoriasis flare-ups may be triggered by a variety of
factors, including environment