People with Complex Regional pain syndrome may exhibit abnormal sensation throughout all or part of the affected area. This often includes increased sensitivity to stimuli such as touch, pressure, or temperature. Desensitization can be an effective way to treat hypersensitivity, especially when used in combination with other medical and/or therapeutic interventions.
Hypersensitivity because of abnormal pain processing
Desensitization is a treatment technique used to modify how sensitive an area is to particular stimuli. This technique is utilized to decrease, or normalize, the body's response to particular sensations.
It is consistent stimulus to the affected area for short periods of time, frequently throughout the day. These small bursts of therapeutic activity shower the brain with sensory input. The brain responds to this demand by acclimating to the sensation, thereby gradually decreasing the body's pain response to the particular stimuli. The body gets used to the stimulus and the stimuli becomes tolerable and no longer elicits the maximal pain response. 
It involves application of "unpleasant" stimuli to the hypersensitive area. These stimuli are the one that the body is routinely exposed to and do not elicit a painful response when presented to non-affected areas of the body, thus they are not harmful or damaging. The items used for desensitization vary, depending on what the affected area interprets as painful. Stimuli may consist of different textures/fabrics, light or deep pressure, vibration, tapping, heat or cold.
Progression of the application
It progresses gradually from stimuli that produce the least painful response to stimuli that produce the most painful response. Once the affected area begins to acclimate to the initial stimulus, the next stimulus is incorporated. For example a desensitization program may progress from a very soft material stimulus (ie, silk) to a rougher material (i.e. wool) or textured fabric (i.e. Velcro). The course of this progression may take several days to several weeks, depending on the level of hypersensitivity.
Desensitization may minimize body's painful response to various stimuli; however the affected area may still feel uncomfortable when in contact with particular stimuli. The goal of desensitization is to inhibit or interrupt the body's interpretation of routine stimuli as painful. It does not assure that these stimuli will become pleasant or enjoyable, but that they will no longer provoke an extreme pain response. There will be tropical changes over the applied part, in order to prevent application of ice coolant spray following the desensitization gives better results. 
Desensitization could be considered as providing corrective tactile input to the affected limb body schema. Traditionally this has been conducted using a range of textured fabrics but more recent research suggests that electrical sensory discrimination training devices may also play a role. The use of various textures applied to the affected skin can provide tactile information regarding the precise shape and size dimensions of the contact area contributing to a more accurate somatosensory representation. Furthermore, encouraging patients to look at the limb at the time of skin contact provides corrective visual input of the limb. Although the effect of desensitization on body perception disturbances has not been researched per se, it would be reasonable to suggest that this intervention may be beneficial as it has been shown to aid the reversal of cortical reorganization.
Normalization of internal body maps undoubtedly should have a direct positive impact on body perception. Desensitization has also been expressed by patients as helpful in perceiving the affected limb in a more normal way.  
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- R. N. Harden. Complex regional pain syndrome; Br J Anaesth 2001; 87: 99–106
- Available from youtube Desensitization Exercises for Complex Regional Pain Syndrome http://youtu.be/Y8dGcY0ig4A
- Cristiana Kahl Collins. Physical Therapy Management of Complex Regional Pain Syndrome I in a 14-Year-Old Patient Using Strain Counterstrain: A Case Report. J Man Manip Ther. 2007; 15(1): 25–41.
- Flor H. The modification of cortical reorganization and chronic pain by sensory feedback. Applied Psychophys and Biofeedback. 2002. 27 (3): 215-225.
- Moseley GL, Zalucki NM, and Wiech K. Tactile discrimination, but not tactile stimulation alone, reduces chronic limb pain. Pain. 2008. 137(3):600-608.