Antiperspirant use and the risk of breast cancer.

The rumor that antiperspirant use causes breast cancer continues to circulate the Internet. Although unfounded, there have been no published epidemiologic studies to support or refute this claim. This population-based case- control study investigated a possible relationship between use of products applied for underarm perspiration and the risk for breast cancer in women aged 20-74 years. Case patients (n = 813) were diagnosed between November 1992 and March 1995; control subjects (n = 793) were identified by random digit dialing and were frequency-matched by 5-year age groups. Product use information was obtained during an in-person interview. Odds ratios (ORs) and 95% confidence intervals were estimated by the use of conditional logistic regression. P values were determined with the Wald chi(2) test. All statistical tests were two-sided. The risk for breast cancer did not increase with any of the following activities: 1) antiperspirant (OR = 0.9; P =.23) or deodorant (OR = 1.2; P =.19) use; 2) product use among subjects who shaved with a blade razor; or 3) application of products within 1 hour of shaving (for antiperspirant, OR = 0.9 and P =.40; for deodorant, OR = 1.2 and P =.16). These findings do not support the hypothesis that antiperspirant use increases the risk for breast cancer.