Why do some people think that antiperspirants might cause breast cancer?
Most cancers occur in the area of the breast closest to the armpit. Also, breast cancer is slightly more common in the left breast, which could be because right-handed people tend to be more heavy-handed with deodorant when using that hand. Breast cancer is more common in countries where a lot of antiperspirant is used. One study found paraben chemicals within breast tumours (Journal of Applied Toxicology 2004;24:5–13), and other research suggest aluminium may affect breast cells (Journal of Inorganic Biochemistry 2007;101:1344–6).