Aluminum-based compounds are used as the active ingredient in antiperspirants. These compounds form a temporary “plug” within the sweat duct that stops the flow of sweat to the skin's surface. Some research suggests that aluminum-containing underarm antiperspirants, which are applied frequently and left on the skin near the breast, may be absorbed by the skin and have estrogen-like (hormonal) effects (3).
Because estrogen can promote the growth of breast cancer cells, some scientists have suggested that the aluminum-based compounds in antiperspirants may contribute to the development of breast cancer (3). In addition, it has been suggested that aluminum may have direct activity in breast tissue (4). However, no studies to date have confirmed any substantial adverse effects of aluminum that could contribute to increased breast cancer risks. A 2014 review concluded there was no clear evidence showing that the use of aluminum-containing underarm antiperspirants or cosmetics increases the risk of breast cancer (5).
Some research has focused on parabens, which are preservatives used in some deodorants and antiperspirants that have been shown to mimic the activity of estrogen in the body’s cells (6). It has been reported that parabens are found in breast tumors, but there is no evidence that they cause breast cancer. Although parabens are used in many cosmetic, food, and pharmaceutical products, most deodorants and antiperspirants in the United States do not currently contain parabens. The National Library of Medicine’s Household Products Database has information about the ingredients used in most major brands of deodorants and antiperspirants.