"Some of these can be time limited but some can last for quite a few years," Casale said.
Most urticarias are treated with antihistamines but Casale said that because they are so rare, there have been no major breakthroughs in treatments.
About one in five people will develop hives at some point in their lives, but a much smaller number will get physical urticarias (urticaria is another word for hives) when they contact or experience some very ordinary things.
"If you put an ice cube on somebody that has cold urticaria, they're going to have a big welt right where the ice cube was," said Casale. And it's not just the cold. "It could be heat, could be sunlight. It could be vibration. It could be pressure."
In fact, some cases of heat-induced hives might be confused with exercise-induced anaphylaxis because exercise can raise body temperature.
Casale found the two could be distinguished for diagnosis by either heating the patient using a warming blanket or placing the patient's hand or leg in hot water. Only those with heat urticaria will develop hives.
An even smaller number of people with the condition may be diagnosed with aquagenic urticaria, meaning they are allergic to water.
"I actually saw a patient probably six or seven years ago. We put water on her and, boy, she just broke out in hives where the water hit her," said Casale, although he thought the reaction might have been provoked more so by the temperature of the water than the water itself.
There's no treatment for physical urticaria and "we still don't have a really good clue as to how [the hives] come about," said Casale. "These syndromes aren't extremely common and they're very difficult to study."
Normally we're pretty careful about the kinds of things we let touch our faces, but how often has that concern come to mind when that thing is your cell phone?
In recent years, dermatologists have begun to see an increasing number of contact dermatitis patients who are allergic to their cell phones, or more specifically the nickel in their cell phones.
"Some people are extremely nickel-sensitive," said Dr. Lionel Bercovitch, a professor of dermatology at Brown Medical School.
Nickel is a metal that's used in a wide variety of products, including jewelry, belt buckles and watch bands. It's the most common cause of contact dermatitis in the developed world.
The symptoms of a nickel reaction range from redness to a more obvious rash, even blisters. Bercovitch suspects some cases involving cell phones are not being reported because the symptoms are being confused with facial eczema.
"My guess is that it's probably more common than we think, but it's just not widely recognized," he said.
Not all cell phones contain nickel. In an attempt to get an idea of how many phones might have the metal, Bercovitch tested 22 models and published the results in the Canadian Medical Association Journal in January 2008.
Ten devices were positive for the metal. In some, the nickel showed up around the menu buttons. In others, it appeared near the decorative logos, around the edge of the screen or on a part of the handset where paint was chipped.
"I think you need the perfect storm of somebody who's allergic to nickel in the first place, and somebody who uses the cell phone a lot, and a cell phone that has an exposed nickel area," said Bercovitch.