Pityriasis

Pityriasis (from the Greek word pityron, 'bran') is the term given to certain of the squamous or scaly diseases of the skin, in which there is a continual throwing off of bran-like scales of epidermis, which are renewed as fast as they are lost. It is most common on the scalp, when it is known as dandruff, and must be treated with weak alkaline lotions, or, if these fail, with diluted white precipitate ointment, provided there is no inflammation. Pityriasis rubra is a severe disease, affecting the whole or almost the whole body, and closely allied to, if not identical with, a severe form of dry Eczema (q.v.). Pityriasis or Tinea versicolor is due to the presence of a parasitic fungus, the Microsporon furfurans; it occurs in the form of irregular yellowish or brownish patches, confined to the parts of the body covered by the clothes. Microscopic examination of the exfoliated scales shows the spores and filaments of the fungus. The treatment of this affection must be solely local. Probably the best remedy is the application of a saturated watery solution of sulphurous acid gas, or of one of the sulphites dissolved in diluted vinegar, or of white precipitate ointment.