I found this about it-
[Hendler Alcohol Drop and Swipe Test (7). In this test, a physician squeezes an alcohol swab so that a drop of alcohol lands on the patient's affected area. If the patient immediately withdraws the limb and complains of a burning pain, the physician has demonstrated thermal allodynia, i.e. a painful response to the cooling effects of a drop of alcohol on a limb. After two minutes, if there has been no response to the thermal test, a patient may begin to experience burning pain in the affected limb. This occurs as the fat soluble alcohol permeates the skin and begins to chemically irritate the hypersensitive C fibers, which conduct the message of pain. If the patient then experiences pain, this demonstrates chemical allodynia. Then, with the leftover alcohol swab, the physician gently strokes the affected area. If this produces pain, this clearly demonstrates mechanical allodynia. In order to establish the diagnosis of RSD (CRPS 1)]
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