The Collaborative International Dictionary of English v.0.48:

Urtication \Ur`ti*ca"tion\, n. (Med.)
   The act or process of whipping or stinging with nettles; --
   sometimes used in the treatment of paralysis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

urtication
    n 1: an itchy skin eruption characterized by weals with pale
         interiors and well-defined red margins; usually the result
         of an allergic response to insect bites or food or drugs
         [syn: urtication, urticaria, hives, nettle rash]
    2: a sensation of having been stung by nettles