An analysis of combined results from multiple studies has not found strong evidence of an increased risk of breast or Bladder cancer among people who dye their hair.

There have been some reports linking use of hair dye with increased cancer risk, the researchers note in this week’s Journal of the American Medical Association.

To evaluate the overall findings from past investigations, Dr. Bahi Takkouche of the University of Santiago de Compostela, Spain, and associates identified 79 studies on hair dye use and cancer.

Twelve studies of breast cancer included 5019 cases and 8486 unaffected controls, while 10 studies of bladder cancer included 5740 cases and 9290 controls. Pooled data from these studies showed no increased likelihood of either cancer connected to using hair dye.

“Globally, there is no effect of personal hair dye use on the risk of breast and Bladder cancer,” the investigators conclude.

In an analysis of 40 studies looking at blood cancer, the authors observed a “borderline increase in the risk” of about 15 percent for people who had ever used hair dye. “The evidence of a causal effect is too weak to represent a major public health concern,” Takkouche and his colleagues maintain.

Although the results were generally negative, the researchers say studies should probably focus on occupations in which exposure to hair dye is more prolonged.

SOURCE: Journal of the American Medical Association, May 25, 2005.