There was redness and itching, some blisters and oozing. Something wasn't right with Dr. Michael Rosenthal's patient, a woman in her mid-50s.
The inflammation around her scalp pointed to some type of allergic reaction, but the patient wasn't sure what had caused it.
"Have you put anything new on your hair or head?" Rosenthal asked her.
She said she had used hair dye, but had discounted the dye as a source of the problem because the symptoms didn't arrive until more than a week after she had colored her hair. But the hair dye turned out to be the culprit.
When you use something new on your body, it might take a week or two to elicit the allergic reaction, explained Rosenthal, vice chairman of academic programs at the department of family and community medicine at Thomas Jefferson University. "Don't think that because you've been using something a long time that it can't be that."
Talk to any physician who treats allergies, and they'll liken their job to that of a police detective. Constantly on the hunt for the unknown offender, an allergy consult often seems more like a witness interrogation featuring a litany of probing questions.
Sometimes, the case is tough to crack, because you can be allergic to just about anything. Some people are even allergic to medications that are used to treat allergies, such as corticosteroids.
Still, seldom are these incidents one-of-a-kind phenomena. Even the most unexpected allergic response is likely to be duplicated in another person, somewhere.
In order to make the job easier for fellow allergy investigators, doctors will publish accounts of rare allergic reactions in medical journals and share their findings at medical conferences and on the Internet.
We've collected 10 of the most unusual allergy stories.
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.