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Shereé Peterson and a party of female relatives were delighted with the swirly, black designs a henna artist had piped onto their hands and forearms at a Minneapolis mall.

Peterson, of Minnetonka, her 5-year-old daughter Sophia and four others had piled into one car just before the New Year and set off to get temporary henna tattoos from the artist, who had been recommended by a Ridgedale store clerk. The group was directed to a booth in Karmel Square filled with colorful scarves and other merchandise. A woman at the back of the booth charged $5 per tattoo.

A week and a half later, as Sophia's tattoo began to fade, an identical design of raised itchy blisters took its place. Peterson soon discovered that an ingredient found in some henna pastes is a strong allergen that is illegal to apply to skin but goes largely unregulated.

"In my mind, I was just thinking, oh, this is henna, which I had known to come from a plant. I didn't think twice about a potential reaction," Peterson said.

The culprit in Sophia's case is a chemical called para phenylenediamine (PPD), a pediatrician told Peterson.

It may also have been the culprit at a eighth-grade graduation party in 2011, when about half of a group of 35 Twin Cities students developed blisters and weeping lesions about a week after an artist used a dark-colored paste to draw henna tattoos on their skin. According to a news release by the Minnesota Department of Health, the children were treated with steroid cream and three were given oral antibiotics. The department, which didn't identify the children, urged customers to check for PPD in henna pastes before getting a tattoo.

Many henna artists mix their own henna paste solutions and some add PPD to darken the staining and lengthen the life of the tattoo. PPD may also be present in pre-mixed henna sold by retailers and may not be properly labeled.

Harbinger of luck

There's a cultural reason behind the tinting of henna, said Dr. Sanober Amin, a resident in the Department of Dermatology at the University of Minnesota. "A darker henna outcome is associated with better luck, especially when it's applied on the hands of a bride," Amin said, referring to the practices of many Southeast Asian and African cultures.

"On the wedding day everybody will come and look at the color intensity of your hands, the henna on your hands, and bless you with good luck or not," said Amin, who got the henna tattoos herself when she was wed in Pakistan.

"We see a lot of patients with allergies to PPD. It's a very common contact allergy," according to Dr. Bethany Cook, a colleague of Amin. Most patients are treated for a reaction to the PPD legally found in about two-thirds of hair dyes, but since the 1990s dermatologists have been seeing more and more cases attributed to henna tattoos, Amin said.

When PPD is laced into henna pastes it is usually at a much higher concentration than that found in hair dye, Cook said.

PPD was even voted the "Contact Allergen of the Year" by the American Contact Dermatology Society in 2006.

Skin exposure to PPD-laced henna can have long-term consequences. A common complication is a lifelong sensitivity to hair dye containing PPD, Amin said. Some patients develop scars and skin discoloration that essentially turn what was supposed to be a temporary tattoo into a permanent one.

Medical literature suggests a small number of exposed patients develop a cross-sensitivity to anesthetics and certain textile and food dyes. In very rare instances, people have died after exposure to PPD.

'Natural henna' artists unite

Though the FDA has not approved henna in its pure form for application on skin, the plant appears to be safe and is widely available on the Internet. "So far we have not seen an allergy to henna itself," Amin said.

Many local henna artists agree and have banded together to promote the safe use of henna. Amy Leinen lives in North St. Paul and started a "temporary body art" business called Mehndi Moments a few years ago.

"I'm networked with a whole bunch of other henna artists who are only using natural henna," Leinen said. "We educate about the dangers of PPD and we're networked throughout the world." There is even a "Minnesconsin" Facebook group dedicated to the use of natural henna, she said.

Leinen, who applies "henna crowns" containing "healing symbols" on the heads of cancer patients, symbolic imagery on pregnant women's bellies and provides tattoos at birthday parties and festivals, said she gets her raw henna from a reliable source and mixes it with lemon juice and essential oils.

PPD-free henna is usually brownish when mixed and bright orange when the paste is removed from the skin, darkening gradually before it fades, Leinen said. Black paste indicates the presence of PPD.

The U.S. Food and Drug Administration regulates most color additives, including PPD. "All color additives used in cosmetics [or any other FDA-regulated product] must be approved by the FDA," according to an information sheet.

The Peterson family filed a complaint with the FDA about the incident. When Whistleblower visited Karmel Square last week, the tattoo artist could not be found.

The FDA failed to respond to requests for an interview, and it is unclear how its regulations are enforced.

The practice does not fall under the jurisdiction of the Minnesota Board of Cosmetologist Examiners because henna artists are not required to be licensed, according to Executive Director Gina Stauss.

The Minnesota Department of Health "does not have a regulatory role monitoring henna art or any adverse reactions to henna," according to Scott Smith, spokesman for the Minnesota Department of Health. "Henna tattoos do not fall under the umbrella of the Minnesota Body Art Statute."

Peterson is crossing her fingers that her daughter will emerge without scarring or a permanent ghost design. "Her doctor told us that most likely by the time summer hits, she'll have some traces of it and it's really important to use sunscreen so that there isn't any discoloration of the skin," Peterson said.