itching associated with many skin disorders and systemic diseases.
stimuli for pruritis
itch is carried by specific unmyelinated c nerve fibers. substance P (neurotransmitter) causes histamine release and wheal formation with itching when injected into the skin. small c receptors are also sensitive to histamine. lymphocytes present in itching skin may be involved in the pathogenesis of itching. stimuli that cause pain also cause itch at lower intensities.