Jan. 26, 2004 -- Long-term use of permanent hair dye -- in dark colors -- doubles a person's risk of certain blood cancers, new research shows.
Earlier studies have linked permanent hair dyes to bladder cancer as well as to the group of diseases known as non-Hodgkin's lymphoma. Non-Hodgkin's lymphoma rates are up all over the world. Nobody knows why, says Yale researcher Tongzhang Zheng, ScD.
Zheng suspected that hair dyes might play a role. Use of hair dye is increasing. And the products -- especially the permanent types in dark colors -- may expose users to dangerous chemicals. So Zheng led a research team that analyzed hair dye use in 601 women with non-Hodgkin's lymphoma and in 717 similar women without cancer.
The results: An increased risk of non-Hodgkin's lymphoma was observed for women who reported the use of hair coloring products before 1980. Women who used dark-colored permanent hair-coloring products for more than 25 years doubled their risk of non-Hodgkin's lymphoma. The risk was nearly the same for women who used more than 200 applications of these products. No increased risk was seen in women who used semi-permanent dyes or temporary rinses.
So should women stop using permanent hair dyes?
"Hair coloring is a personal decision for all kinds of reasons," Zheng tells WebMD. "But if I am the person, if semi-permanent or temporary dyes could serve my issue, I would do it. Because these contain much less of the ingredients linked to cancer."
Zheng's report appears in the Jan. 15 issue of the American Journal of Epidemiology.
Industry Says Hair Dye Safe
In a letter to WebMD, the Cosmetic, Toiletry, and Fragrance Association points to a 2000 review of the scientific literature on hair dyes and cancer by Johns Hopkins researchers. That study found the evidence linking hair dyes to cancer to be inconclusive. It called for further research using improved methods.
The CTFA statement also points to two large epidemiologic studies that found no link between hair dyes and cancer.
"The safety of hair dyes is supported by the overwhelming wealth of scientific research, including several well-designed studies conducted by prestigious institutions such as the American Cancer Society and Harvard University," the CTFA notes. "These large epidemiology studies include more than 570,000 and 120,000 women respectively, and showed no elevated health risk for women using hair dyes."
"The hair color industry reaffirms its confidence in the safety of hair dyes."
Zheng and colleagues, however, note that two other large epidemiological studies reached different conclusions. They suggest that all of these studies were limited by methodological problems that may have underestimated exposure to hair dye.
Zheng says the cosmetic industry has been very helpful in providing information helpful to researchers.
Are Today's Products Safer?
Zheng's team found no increased non-Hodgkin's lymphoma risk in women who began coloring their hair after 1980. That raises a serious question. In 1979, the hair care industry drastically changed the formulation of most hair dyes to remove known cancer-causing agents.