Henna hazard: Chemical causes ornate allergies
Harsh dye can swell popular tattoos into itchy, blistery swirls and shapes
The American Academy of Dermatology recently issued a warning that a chemical found in black henna tattoos can cause a severe allergic reaction, causing the skin to redden, swell and blister — but only where the henna is applied, leaving people with bubbly blisters in shapes like suns, stars and flowers.
As henna body art has become mainstream in the last few years, often peddled at summer carnivals and concerts, dermatologists report increasingly treating patients, especially teen girls and young women, with these often elaborate looking allergic reactions.
“Just because they’re temporary, people think they’re safe,” says Dr. Sharon E. Jacob, a dermatologist at the University of California, San Diego.
Natural henna vs. black henna
While true henna is made from harmless plants, black henna uses a chemical called para-phenylenediami ne, or PPD, which makes the tattoo dry quickly and last longer — and in some cases, that’s much, much longer.
“These skin allergies themselves are not dangerous,” says Dr. Colby Evans, a dermatologist in private practice in Austin, Texas. “But they can cause scarring or darkness to the skin that can be permanent."
Despite the potential for creating a permanent souvenir from that trip to Mexico, the scarring generally will go away on its own within a few weeks. But it's almost always odd-looking. This week, the New England Journal of Medicine published Evans’ account of a particularly intense case: A 19-year-old Kuwaiti woman Evans treated after she returned from a wedding, where she had black henna applied to her forearms, hands and fingers. A week later, her swirly, flowery henna was overwritten with a swirly, flowery blister.
Last year, Evans also treated a young man with a similar allergic reaction to henna that took an even more bizarre form: a blister on the back of his neck in the perfect shape of an eagle.
In both cases, Evans prescribed steroid creams to bring the swelling down.
Lifelong allergies to some medications
But Evans and other dermatologists warn that just one bad reaction to black henna can be enough to cause permanent sensitivity to PPD, and that allergy can cross-react with chemical relatives in certain anesthetics and medications for heart disease, hypertension and diabetes.
“The allergy you can develop is lifelong,” says Jacob. But she’s found that people, especially teens, are generally unimpressed by her warnings of reactions to medication, so she reserves this for the kicker: “It may mean you can never dye your hair again.”
While PPD is used in most hair dyes, allergic reactions aren’t very common because it isn't applied directly to the skin, and in black henna the concentration of PPD is 10 times higher, Jacob estimates. But a PPD sensitivity could cause an allergic reaction after even the slightest contact with the chemical.
Kim Geiger's blister faded away within a month, and her mom says she hasn't had any allergic reaction to medication since. But Debbe Geiger often wonders how anyone could ever tell the difference between safe, natural henna and black henna.
“This was a little booth set up at the hotel pool, and I didn’t think anything of it,” she says.
Experts say there are a few easy ways to tell the difference between true henna and black henna. For one, henna is never black — it’s red, which darkens to a brownish color on the skin as it dries. Real henna starts to fade away within a few days, so be wary of a henna tattoo artist who boasts of tattoos that will last any longer than that.
But both mom and daughter Geiger aren’t taking any more chances; they’re staying far away from all things henna. “It looks so harmless," Debbe Geiger says, "but you have to watch these ingredients they’re using.”
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