The Collaborative International Dictionary of English v.0.48:

Numb \Numb\, v. t. [imp. & p. p. Numbed (n[u^]md); p. pr. &
   vb. n. Numbing (n[u^]m"[i^]ng).]
   To make numb; to deprive of the power of sensation or motion;
   to render senseless or inert; to deaden; to benumb; to
   stupefy.
   [1913 Webster]

         For lazy winter numbs the laboring hand. --Dryden.
   [1913 Webster]

         Like dull narcotics, numbing pain.       --Tennyson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

desensitizing \desensitizing\ adj.
   making less susceptible or sensitive to either physical or
   emotional stimuli. Opposite of sensitizing. [Narrower
   terms: numbing]
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

numbing
    adj 1: causing numbness or insensitivity; "the numbing effect of
           grief"

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "numbing":
   Siberian, abatement, algid, allayment, alleviating, alleviation,
   alleviative, analgesia, analgesic, anesthesia, anesthetic,
   anesthetizing, anodyne, appeasement, arctic, assuagement,
   assuasive, balmy, balsamic, below zero, benumbing, biting, bitter,
   bitterly cold, bleak, boreal, brisk, brumal, cathartic, cleansing,
   cold, cold as charity, cold as death, cold as ice, cold as marble,
   crisp, cutting, deadening, demulcent, diminishment, diminution,
   dulling, ease, easement, easing, emollient, freezing,
   freezing cold, frigid, gelid, glacial, hibernal, hiemal,
   hyperborean, ice-cold, ice-encrusted, icelike, icy, inclement,
   keen, lenitive, lessening, lulling, mitigating, mitigation,
   mitigative, mollification, narcotic, nipping, nippy, pain-killing,
   palliation, palliative, penetrating, piercing, pinching, purgative,
   raw, reduction, relief, relieving, remedial, remedy, rigorous,
   salving, severe, sharp, sleety, slushy, snappy, softening,
   soothing, stone-cold, stunning, stupefying, subduement, subduing,
   subzero, supercooled, winterbound, winterlike, wintery, wintry