Pruritus Flashcards
why is a itch non adapting
doesnt settle when you itch it
what in the skin carries the itch sensation
nerve fibres (unmyelinated c fibres)
what can mediate itch
chemicals in skin (histamine, PGE2, acetylcholine, serotonin)
nerve transmission (unmyelinated c fibres)
CNS mediators (opiates- endogenous and exogenous)
what is the main mediator of itch
histamine
what can cause mast cell degranulation
allergen, anti-IgE, substance P, stem cell factor, codeine, C5a, anti- FCERI
what mediators are released by mast cell degraulation
pre formed
- proteases
- heparin
- histamine
- cytokines
newly formed
- prostaglandins
- leukotrienes
- platelet activating factor
what is pruritoceptive
something (usually associates with inflammation and dryness) in skin that triggers itch
what is a neurogenic itch
no evident damage in CNS, itch caused by e.g. opiate effects on CNS receptors
what is a neurpathic itch
damage to central or peripheral nerves causing itch
what is a psychogenic itch
psychological causes with no detectable CNS damage (dellusions of infestation)
give examples of pruritoceptive itches
insect bites, eczema, lichen planus, psoriasis,
what diseases are associates with neurogenic itch- give examples
systemic- liver and bile duct, psychogenic, kidney, thyroid, haematological diseases, paraneoplastic diseases
e.g. PBC
what are non specific anti itch treatments
sedative anti histamines emollients antidepressants phototherapy opiate antagnists
