The idea that deodorant causes breast cancer has been regarded as an urban legend for years. Now one Northwestern researcher says his research shows underarm shaving is the missing link between the two — but other researchers have widely criticized the study.

Dr. Kris McGrath, an associate professor at the Feinberg School of Medicine, analyzed the questionnaires of 437 breast cancer patients and concluded that the combination of heavy antiperspirant deodorant use and frequent underarm shaving in women could lead to a breast cancer diagnosis at an earlier age.

McGrath found that heavy deodorant users in his study were diagnosed with breast cancer 22 years earlier than non-users.

But other cancer researchers have criticized the study, which was published in the European Journal of Cancer Prevention.

Dr. Dana Mirick, a cancer researcher at the Fred Hutchinson Cancer Research Center in Seattle, wrote in an e-mail to The Daily that McGrath’s study had limitations that “render it incapable of providing any quantitative estimate of the risk of breast cancer associated with antiperspirant use or shaving behavior.”

Mirick — who conducted her own study in 2002 showing no link between breast cancer and deodorant — said the most significant flaw in McGrath’s study was that it lacked a control group, meaning that McGrath did not analyze a group of women who used deodorant but were not diagnosed with breast cancer.

Mirick also said the sample size of 437 people was too small to draw scientific conclusions.

But McGrath defended his research, saying previous studies such as Mirick’s did not consider the intensity of deodorant use while his study did.

“More work needs to be done,” McGrath said. “But it’s a pilot study that shows a possible link to support more (research).”

McGrath said he believes aluminum salts — an ingredient in many antiperspirants that promotes dryness — might cause breast cancer. Shaving under the arms can make it easier for these compounds to pass through the skin, according to McGrath’s study.

The notion that deodorant could cause breast cancer has been thought of as an urban legend. According to Mirick, a rumor about the link probably started on the Internet in the early 1990s.

Weinberg senior Jessica Herman said she first heard the rumor about deodorant causing breast cancer through a friend in elementary school.

“It’s always been in the back of my mind,” Herman said. “I have always checked since then if my deodorant is an antiperspirant.”

Leena Palamkunnel, a Weinberg junior, said she had never heard the rumor, but the issue concerned her.

“I have a history of breast cancer in my family,” Palamkunnel said. “If it was a valid study, it definitely would definitely have me reconsider using (deodorant containing antiperspirants).”

McGrath recommended that concerned women use non-antiperspirant deodorants and wait 24 hours after shaving to apply an antiperspirant.