Published Online: September 6, 2014
Physical urticaria is a unique form of hives that is provoked by exposure to specific environmental or physical stimuli such as cold, pressure, heat, or vibration, or in some cases from exercise. It is estimated that 0.5 % of the population will develop hives from one of these triggers. Resolution of symptoms is quite variable and depends on the type of physical urticaria, age of onset, and severity, but overall it is estimated that 50% of patients will no longer suffer from these hives after 5 years. Notably, diagnosis is generally based on patient history, but may be confirmed by office-based testing using the stimuli reported to produce a hive.
In a study recently published in The Journal of Allergy and Clinical Immunology: In Practice, Komarow and colleagues explore the consistency between patients’ history of physical urticaria and the results of challenge testing. For this study, they examined a cohort of 76 patients already diagnosed as having physical urticaria, most of who were on medications and had altered their lifestyle to avoid reactions. A total of 294 challenge tests were performed, revealing that approximately 1/3 of the patients referred with the diagnosis of a specific physical urticaria were negative to challenge. These findings remained consistent upon follow-up at least one year later.
These findings were generally unexpected and enabled those in the negative challenge group to decrease medication use, and in some cases, with proper monitoring, to stop medicine and resume normal activities. These results support the value of challenge testing in patients with a history of a physical urticaria and suggest the need to re-evaluate at intervals to determine if the physical urticaria once present has spontaneously resolved.
Standard challenge testing provides an objective diagnosis and establishes individual thresholds for positivity, which can be used to determine disease severity and objectively evaluate response to therapy. One option for physicians who do not perform testing—and where the diagnosis of a physical urticaria is associated with behavior intervention and pharmacologic therapy—is to consider referral to a specialty clinic or tertiary care center for challenge testing.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.