 Thus, thermography alone cannot be used as conclusive evidence for—or against—a diagnosis of CRPS and must be interpreted in light of the patient's larger medical history and prior diagnostic studies.In order to minimise the confounding influence of external factors, patients undergoing infrared thermographic testing must conform to special restrictions regarding the use of certain vasoconstrictors (namely, nicotine and caffeine), skin lotions, physical therapy, and other diagnostic procedures in the days prior to testing.Patients may also be required to discontinue certain pain medications and sympathetic blockers.