Hives that are caused by body and environmental triggers are known as physical urticarias and include:
- Cold-Induced: Here, it is the stimulus of cold that brings on the urticaria, and this can include drinking cold beverages or swimming in chilly water. Avoidance, warm dressing and antihistamines are usually prescribed.
- Solar Hives: Heading South for the Winter? Some people develop urticaria from a reaction to the sun’s UVA and UVB rays. Avoidance of direct sun, including protective dressing and using a sunblock are important.
- Pressure Hives: Those affected will get hives about six hours following constriction from clothes or belts. Tight clothing needs to be avoided and antihistamines can offer relief.
- Heat-Stimulated: In the condition known as cholinergic urticaria, itchy hives will form when body temperature rises by a few degrees. Sometimes people think they are allergic to their perspiration or exercise, but body temperature is the real issue. Avoidance of over-heating and antihistamines are the treatments.
- Water-Stimulated: Aquagenic Urticaria, which Alexandra Allen wrote about for Allergic Living magazine, is rare. Avoidance measures and antihistamines are important. As well, patients should avoid sudden exposure to temperature change, such as swimming in a cold lake. For reactions not limited to the skin, an epinephrine auto-injector should be prescribed and carried.
What are they? Physical urticarias are an allergic-like reaction, in that the various triggers will set off an immune system response that involves the release of histamine and other chemicals that create the itchy hives and sometimes swelling.
These urticarias are related to the condition known as chronic urticaria, but a key difference is that the chronic hives may not have clear triggers. They can be caused by conditions including: undiagnosed allergies (to food, pets, etc.), autoimmune or hormone disorders and bacterial infections. With chronic hives where triggers haven’t been identified, some patients have had encouraging results with the drug omalizumab (known by the brand Xolair), and other treatments are being investigated. Otherwise, antihistamines are used daily.
It has been challenging to gauge the prevalence of chronic urticaria, but a team of Montreal scientists has produced an analysis of 10 international studies in May 2015. The review, published in Postgrad Medicine, found that chronic urticaria is estimated to affect as many as 3 percent of adults and 0.5 percent of children. More than 1 in 10 of these cases of chronic hives (13 percent) are physical urticarias, according to allergist Dr. Moshe Ben-Shoshan, a co-author of the analysis.
“Increased awareness of the symptoms as well as getting a proper diagnosis and treatment are crucial to improving the lives of those with physical urticarias,” he says.