Pruritus is a topic covered in the 5-Minute Emergency Consult.

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  • Unpleasant sensation that provokes a desire to scratch
  • Mediated by unmyelinated C fibers in upper portion of dermis:
    • Transmitted to dorsal horn of spinal cord
    • Via spinothalamic tract to cerebral cortex
  • Peripheral mediators (e.g., histamine and peptides such as substance P that release histamine) stimulate C fibers and induce itching
  • Prostaglandins (PGE2, PGH2) lower threshold to pruritus
  • Opiates cause pruritus by acting on central receptors
  • No single pharmacologic agent effectively treats all causes of pruritus
  • “Itch–scratch–itch” cycle:
    • Itching triggers scratching
    • Scratching damages skin and stimulates nerve endings, thereby producing even greater itching


4 categories in proposed itch classification:
  • Pruritoceptive: Generated in the skin from localized irritation or inflammation
  • Neurogenic: Generated in the CNS due to circulating pruritogens
  • Neuropathic: Due to CNS or PNS lesions
  • Psychogenic

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