Hair-color products and risk for non-Hodgkin's lymphoma: A population-based study in the San Francisco Bay area

Objectives. As part of a large, epidemiologic study of non-Hodgkin's lymphoma, this study investigated a possible association between use of hair-color products and non-Hodgkin's lymphoma. Methods. A population-based case-control study was conducted in the San Francisco Bay area. Of 4108 participants, 2544 were questioned about use of hair-color products. Control subjects were identified by use of random-digit dialing. Results. Ever use of hair-color products was reported by 56% of case and 56% of control women and 10% of case and 9% of control men. Risks were not elevated for women for use of any hair-color products. Men who ever used semipermanent hair color had slightly elevated risks for non-Hodgkin's lymphoma, with trends associated with greater lifetime frequency of use and frequency of use per year, although individual confidence intervals overlapped unity. These elevated risks were diminished with exclusive use of semipermanent products, and confidence intervals overlapped unity. Conclusions. Integration of our results with those from experimental animal studies and other epidemiologic studies provides little convincing evidence linking non-Hodgkin's lymphoma with normal use of hair-color products in humans.