Pityriasis

n.
  1. (Med.) A superficial affection of the skin, characterized by irregular patches of thin scales which are shed in branlike particles.
  2. (Veter.) A disease of domestic animals characterized by dry epithelial scales, and due to digestive disturbances and alteration of the function of the sebaceous glands.
    3. Pityriasis versicolor
    (Med.), a parasitic disease of the skin, characterized by the development of reddish or brownish patches.