We all want to look younger, but at what price? Chemical peels can make you look younger, but beware: putting strong acids on you skin may also have unwanted affects. That's because a compound commonly used in many peels, called trichloroacetic acid, or TCA, has been linked to cancer. This past summer, the International Agency on Cancer Researched classified TCA as a suspected human carcinogen, and the state of California listed the acid on its state registry of toxic substances. Scientists are quick to say that they're not sure of the real risks of TCA yet, but that alone should be a cause for concern.

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"The short answer is, nobody knows," said Dr. Michael Hadley, an associate professor of dermatology at the University of Utah and a co-author of a chapter on TCA in the Color Atlas of Chemical Peels. "I can tell you that the link is not proven or shown in any human studies. But that's partly because we haven't done the long term research that would give us all the answers."

The link to cancer, says Dr. William Coleman, the editor and chief of the journal Dermatologic Surgery, was shown only in longterm exposures in lab animals, not in humans. But testing long term exposures in humans is ethically murky, which makes it difficult to ensure that a compound like TCA has been sufficiently tested. "Cancer is complicated, exposures are complicated, and it's ethically difficult to do the kinds of human studies that might tell us what we really want to know," said Caroline Cox, research director of the Center for Environmental Health. "In the universe of chemical compounds used in commerce, there are so few that have been thoroughly tested."

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While more testing is done, Dr. Hadley advocates on behalf of caution. "I think there's a certain amount of care that should be used." [New York Times]