Breast and prostate cancer share similarities and likely represent homologous cancers in females and males, respectively. The role of hormones such as testosterone and estrogen in carcinogenesis is well established. Despite worldwide research efforts, the pathogenesis of these diseases is largely not well understood. Personal care products containing estrogens or xenoestrogens have raised concern as a breast cancer risk, especially in young African-American women. In the United States (US) there is a parallel rise in the incidence in breast and prostate cancer compared to selected non-hormone dependent tumors. Observed US and global breast and prostate cancer incidence increases were occurring before exogenous hormone replacement and xenoestrogen exposure were commonplace. An unintentional, inadvertent, and long term hormone exposure may occur from transdermal absorption of sex hormones and pheromones (androgens) from axillary apocrine sweat gland obstruction by aluminum-based antiperspirants. The global rise in antiperspirant use parallels rises in breast and prostate cancer incidence and mortality rates. A multi-disciplinary literature based set of evidence is presented on how such a link is possible, to prompt confirmatory investigations in the pursuit of unmet needs in breast and prostate cancer etiology and prevention.