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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.
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