Aluminum salts in antiperspirants can mimic estrogen and may accumulate in breast tissue; causal link to breast cancer unproven

This review examined the hypothesis that aluminum-based compounds in underarm antiperspirants contribute to breast cancer development. The author presented evidence that aluminum salts can interfere with estrogen receptor function and that aluminum has been detected in breast tissue. The disproportionate occurrence of breast tumors in the upper outer quadrant (nearest to the underarm) was cited as suggestive but not conclusive evidence. The review noted that no epidemiological study had established a causal relationship. Despite the lack of definitive proof, this hypothesis drove consumer demand for aluminum-free deodorants and remains a cornerstone concern in clean personal care.

Genesis Appeal (UK breast cancer charity)