Sept. 25 -- Celebrities like Madonna and Uma Thurman have brought temporary henna "tattoos" into vogue, and now those who want the look can get henna painted onto their bodies in special booths and tattoo parlors across the country.
But even more popular are so-called black henna tattoos, which are popping up everywhere from Florida's beaches, to shopping malls, to an outdoor stand right in front of the Good Morning America studios in Times Square.
Black henna is advertised as a fun, temporary decoration that, because of its dark stain, looks like a real tattoo. It is supposed to last only one to three weeks, but some people are getting a nasty surprise after they've paid for their new look.
Joey Vitello, 6, of Newport Richey, Fla., got a black henna tattoo earlier this summer at a beach in Clearwater, Fla. At first he loved it, but soon, to his parents' shock, it became a health issue.
"I was scared. I thought maybe, you know, he had an infection or something," said his mother, Doreen Vitello. "It started stinging, but I didn't think anything of it, and he didn't make a major big deal about it. As the days went on, it just spread. It was horrible. It was all red, blisters, swollen, oozing. It was terrible."
Now Joey has a scar that his doctor says may be permanent.
Warnings in Canada, Florida
In August, Health Canada warned Canadians about the potential danger posed by black henna, which isn't pure henna at all. Much of the time, it's mixed with commercial hair dye, which includes a chemical called p-phenylenediamine, or PPD.
But in the United States, concern over the safety of black henna tattoos has been prevalent only in areas where the tattoos are readily available. Communities in Florida have tried to keep on top of tattoo artists on beaches and streets and the Florida State Department of Health even issued a warning over the summer.
Doctors at New York University School of Medicine have studied black henna and its ingredients.
"The hair dye when mixed with henna accelerates the dyeing process," said NYU's Dr. Ronald Brancaccio. "So instead of taking two to six hours to dye the skin, it only takes minutes."