Temperature testing in a patient with cold urticaria using TempTest 4.0

(A) The TempTest 4.0 is a thermoelectric device that is commercially available. It contains a U-shaped metallic element that is placed against the skin and generates temperatures varying from 4 to 44°C. It is used to diagnose cold urticaria (and heat urticaria) and to determine critical temperature thresholds. Threshold information is useful in monitoring a patient's response to therapy.
(B) To perform provocation testing, the volar side of the forearm is laid firmly onto the device along the temperature applicator so that there is no airspace between the device and the forearm and the temperature applicator has close contact to the skin along its entire length. The application time is 5 minutes, after which the patient removes the forearm from the device and the marks from the temperature curve (warm end of applicator and cold end of the applicator) are noted using a skin marker.
(C) The reading is performed 10 minutes after the end of the test procedure. An evaluation template (transparent film) is laid on the patient's forearm based on the position of the temperature applicator so that the markings on the skin and the film are lined up. The contours of the wheal are traced onto the evaluation template using a waterproof permanent marker.
(D) The transparent film then serves as a permanent record of the test results. The threshold temperature or the temperature below which symptoms appeared was 18°C in this patient.