Life-threatening allergic reactions are triggered by heat and exertion

Published Online: November 24, 2015

Generalized hives may be caused by many triggers, including foods, drugs and insect stings. Patients may also develop hives when exposed to physical stimuli. These so-called physical urticarias may be caused by exposure to heat, cold, pressure, exercise and sunlight. For the most part, these reactions involve only the skin and they tend to be mild and self-limited. However, some patients may develop full-blown anaphylactic reactions with physical urticaria, but there are few such reports in the published literature.

Vadas and colleagues recently reported in The Journal of Allergy and Clinical Immunology: In Practice a series of patients with moderate to severe anaphylactic reactions triggered by exposure to high ambient temperatures, strenuous exertion and stress. This study in the Journal of Allergy and Clinical Immunology: In Practice described a total of 19 such patients, of whom 80% were female. Most patients were young adults with a mean age of onset of 27.5 years, but some as young as 12. These patients reported frequent reactions, averaging about one reaction per month. All patients had skin rashes, and most had respiratory distress (80%) and a fall in blood pressure (79%). Almost half of the patients had severe anaphylactic reactions as determined by a standardized scoring system. All patients (100%) reported reactions triggered by high ambient temperatures (such as a hot room, sauna, hot summer day), while almost 90% reported reactions triggered by strenuous exertion.

Investigations were done to rule out other causes of anaphylaxis. One patient underwent a provocation challenge in a sauna. Her typical symptoms of anaphylaxis were reproduced by elevating her core body temperature over 15 min., even without physical activity.

Anaphylactic reactions triggered by elevated core body temperature are uncommon, and generally not readily recognized. Vadas reports that the typical delay between onset of these reactions and diagnosis may be as much as 4 – 5 years. These reactions are typically severe and may be life-threatening.  Increased awareness of this condition will aid prompt diagnosis and minimize the risk of life-threatening anaphylaxis.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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