Those interested in the preventive aspects of the so-called psychosomatic skin reactions need to consider the central fixation phenomenon. This phenomenon has been seen before in instances of painful phantoms which occur after amputation. It is seen also in postherpetic neuralgia; here we have observed failure of relief of pain even with such vigorous peripheral measures as cord section. This same type of central fixation phenomenon can occur in chronic pruritic dematoses as a central fixation of "perceptability of itching."
In the analysis of the background of the persistence of chronic pruritic dermatoses there are certain phases to be considered. One is the local structural change in the skin which makes for continued stimuli of itching sensation. This structural change is associated with acanthosis, fibrosis, chronic inflammation, and local neural changes. These changes then can cause endogenous stimulation of the so-called itch point of Shelley and Arthur1