Itch Flashcards
What is pruritis/itch?
A usually unpleasant, poorly localised, non-adaptive sensation that provokes the desire to scratch
What 3 things mediate itch?
Chemical mediators in the skin
Nerve transmission
Central nervous system
What chemical mediators in the skin mediate itch?
Histamine
PGE2
ACh
Serotonin
What fibres mediate itch?
Unmyelinated C fibres
What in the central nervous system mediates itch?
Opiates
What things cause mast cells to degranulate?
Allergen Anti-FceR1 Anti-IgE Substance P Stem cell factor C5a Codeine
What mediators are released when a mast cell degranulates?
Proteases Heparin Histamine Cytokines Platelent activating factor Leukotrienes Prostaglanding D2
What are the 4 causes of itch?
Pruitoceptive
Neuropahtic
Neurogenic
Psychogenic
What is pruitoceptive itch?
Something in the skin that triggers itch
e.g. Insect bite reaction
What is neuropathic itch?
Damage of any sort to central or peripheral nerves causing itch
What is neurogenic itch?
No evident damage in the CNS but itch is caused by something acting on the CNS
What is psychogenic itch?
Psychological causes with no CNS damage
What is the basic management of itch?
Determine cause where possible
Treat the cause
Anti-itch treatments
What are some anti-itch treatments?
Sedative anti-histamines Emollients Anti-depressants Phototherapy Opiate antagonists
