No, according to a new study by epidemiologist Lynn Rosenberg of Boston University’s Slone Epidemiology Center. Rosenberg and her team studied 48, 167 black women from all over the country who replied to questionnaires mailed out every two years. The women in the Black Women’s Health Study were aged 21 to 69 when the study began in 1995. Rosenberg tracked what happened to women who used hair relaxers containing lye (sodium hydroxide) or calcium hydroxide, guanidine carbonate or thioglycolic acid between 1997 and 2003.

“These substances are not known carcinogens, but because the US Food and Drug Administration does not monitor all ingredients in cosmetics, there is no way to tell for certain that hair relaxers are safe. These products are so widely used by black women that we felt it was important to do our study,” she said. “We found absolutely no increased risk of breast cancer with hair relaxers,” she added.

There’s a caveat in all this, however, noted Judy Norsigian, executive director of Our Bodies, Ourselves, the Boston-based feminist health group. “The study does not answer questions about much longer term use of hair relaxants, nor does it look at particular brands of hair relaxants, some of which might contain especially toxic ingredients.”

The Environmental Working Group, a Washington, D.C.-based research group, rates 101 hair relaxers on one segment of its website, www.cosmeticdatabase.com. Many received unfavorable scores because they contain ingredients whose breakdown products have, in some cases, been linked to cancer, but no specific hair relaxer has been shown to cancer, said Kristan Markey, a chemist and research analyst for the group. “The FDA needs the power to make the cosmetics industry prove its products are safe.”