Pruritus Flashcards
Define pruritis/itch
A usually unpleasant, poorly localised, non-adapting sensation that provokes the desire to scratch
What are the 4 causes of itch?
Pruritoceptive
Neuropathic
Neurogenic
Psychogenic
What is a prurioceptive itch?
something (usually associated with inflammation or dryness) in skin that triggers itch (exposure of unmyelinated C fibres in eczema)
What is a neuropatahic itch?
Damage of any sort to central or peripheral nerves causing itch
What is a neurogenic itch?
No evident damage in CNS but itch caused by, e.g., opiate effects on CNS receptors
What is a psychogenic itch?
Psychological causes with no (currently detectable) CNS damage, e.g. itch in delusions of infestations
Give 3 causes of prurioceptive itch?
Insect bites
eczema
lichen planus
psoriasis
Give examples of a neuropathic itch
multiple sclerosis, pontine stroke, after herpes zoster (shingles)
What can be used to manage itch?
Determine cause if possible
treat cause
anti-itch treatments (anti-pruritic)
Give examples of anti-pruritics
Sedative anti-histamines
emollients with menthol or cooled in fridge
What are the chemical mediators of itch?`
histamine, PGE2, acetylcholine, serotonin, kallikrein, interleukin 2, substance P tryptase
what mediates itch in nerve fibres?
Unmyelinated C fibres
What is a mediator of itch in the central nervous system?
Opiates (endogenous and exogenous)
