An improved Peltier effect‐based instrument for critical temperature threshold measurement in cold‐ and heat‐induced urticaria

Background Cold‐ and heat‐induced urticaria are chronic physical urticaria conditions in which wheals, angioedema or both are evoked by skin exposure to cold and heat respectively. The diagnostic work up of both conditions should include skin provocation tests and accurate determination of critical temperature thresholds ( CTT ) for producing symptoms in order to be able to predict the potential risk that each individual patient faces and how this may be ameliorated by therapy. Objective To develop and validate Temp Test ® 4, a simple and relatively inexpensive instrument for the accurate determination of CTT which may be used in clinical practice. Methods Temp Test ® 4 has a single 2 mm wide 350 mm U‐shaped Peltier element generating a temperature gradient from 4 °C to 44 °C along its length. Using a clear plastic guide placed over the skin after provocation, CTT values may be determined with an accuracy of ±1 °C. Here, Temp Test ® 4 was compared with its much more expensive predecessor, Temp Test ® 3, in inducing wheals in 30 cold urticaria patients. Results Both Temp Test ® 4 and Temp Test ® 3 induced wheals in all 30 patients between 8 ° and 28 °C. There was a highly significant ( P  < 0.0001) correlation between the instruments in the CTT values in individual patients. Conclusion The Temp Test ® 4 is a simple, easy to use, licensed, commercially available and affordable instrument for the determination of CTT s in both cold‐ and heat‐induced urticaria.