While PPD in small amounts is still allowed in hair dyes, it has been banned from skin products in the United States since 1938. Still, henna artists hoping to capitalize on the popularity of the black coloring can mix the dangerous paste on their own.
"When you see somebody with a stand that says 'henna,' ask them what color the stain is when the paste comes off the skin," explained Catherine Cartwright-Jones, a retired henna artist and webmaster for the Henna Page. If the stain on your skin is black, "you've got a problem."
When we think of food allergies, we typically envision a reaction that results after the allergic person puts the problematic food in his or her mouth. But that's not always how it goes.
Dr. Clifford Bassett, an allergy specialist at the Long Island College Hospital and the American Academy of Allergy, Asthma and Immunology, notes that 40 percent of food allergy reactions come not from eating a food trigger but from touching or inhaling it.
Such was the case with one of Bassett's patients, a young girl who developed hives after she hugged and kissed her father when he returned home from work.
"My job is to be sort of an investigative reporter," explained Bassett. "One of the things that we look at is contacts, things we put on the body."
In this case, it wasn't even something the daughter had put on herself. It turned out that the child was allergic to the nut-derived oil in her father's shaving cream, said Bassett.
"That was an episode of a food allergen present in a cosmetic, basically," said Bassett, who added that the problem went away after dad switched to another type of shaving cream.
They were special dairy-free chocolate chips. They weren't supposed to trigger an allergic reaction in Stefania Paciocco's son Gabriele, who at 5 years old already had a laundry list of food allergies including milk, tree nuts, peanuts and eggs.
"I would make a [cookie] batter without eggs in it and I would add [the dairy-free] chocolate chips," said Paciocco, who lives in Plymouth, Mich. "Whenever he would eat anything with these chocolate chips in it, he would start to scratch his throat."
Paciocco suspected her son was allergic to chocolate, but the boy's doctor did not initially believe it.
"Even I was skeptical," said Dr. Harvey Leo, a pediatric allergist and immunologist at C.S. Mott Children's Hospital in Ann Arbor, Mich. "Chocolate allergies are really rare," he explained, adding that most reactions to chocolate either are not true allergic reactions or they come as a result of exposure to nuts or milk in the chocolate chunks.
However, after some persistence by Paciocco, a skin test and a food challenge showed Gabriele, indeed, had the allergy.
"I was shocked because I love chocolate," said Paciocco. "And I felt bad. He can't have a chocolate bar?"
In the end, both parent and doctor agreed persistence paid off in confirming an unusual and potentially dangerous allergy.
"I don't think patients should be afraid to challenge their doctor," said Leo.
"Dr. Leo and I have a really good relationship, so I feel really comfortable with him," added Paciocco. "You should always listen to that intuition."
It's the perfect excuse: I can't exercise because I'm allergic to it.
Sure, it sounds like a joke but a rare condition called exercise-induced anaphylaxis can result in an allergic reaction during exercise, and it can be severe enough to kill the exerciser.