Like cadmium and copper, aluminum is classified as a metalloestrogen, a metal with estrogenic properties. And like cadmium and copper, aluminum appears to be a breast carcinogen, although not all studies are in agreement. Now a review of available research has concluded that it may be best to avoid aluminum-containing antiperspirants.

Sources of aluminum exposure

Most antiperspirant sprays, sticks, and roll-ons incorporate aluminum chlorohydrate or another aluminum salt to block the secretion of sweat. The aluminum in such preparations has been shown to enter through the skin in small amounts and accumulate in all types of breast tissue, including in the upper outer quadrant where many tumors arise. Deodorants, which do not prevent sweating, do not contain aluminum.
The quantities of aluminum entering into circulation through the skin are generally tiny, with the highest exposures generated by spray antiperspirants, followed by sticks, then roll-ons. Applying an antiperspirant to skin that is scraped, cut or irritated (such as may occur after shaving) can result in far higher exposures. The implication is that it is better to use aluminum-containing roll-on or gel antiperspirants rather than sprays or solids. In addition, such antiperspirants should not be applied right after shaving. It also makes sense to apply as little of these products as necessary and not to apply them more than once per day.
Other common sources of aluminum exposure include antacids, baking powder, and the use of aluminum cookware, moka pots, utensils, packaging and containers. Acidic foods and liquids significantly increase aluminum leaching and absorption.

Aluminum and breast cancer

Several studies have reported that aluminum can induce DNA damage at concentrations typically found in human breast tissue. For example, aluminum salts have been shown to damage DNA and compromise the functioning of tumor suppressor genes (including BRCA1 and BRCA2) in normal breast cells. Aluminum has also been shown to interfere with the functioning of estrogen receptors of breast cancer cells. In addition, aluminum has also been shown to cause oxidative damage to cellular components and to induce inflammatory responses within the breast. The presence of aluminum also appears to alter iron metabolism in breast tissue, increasing iron levels, with unclear consequences.
Furthermore, aluminum appears to promote metastasis. One study demonstrated that aluminum increased both the migratory (ability to move freely and distance moved) and invasive properties of hormone receptor positive (ER+/PR+) breast cancer cells. In the study, this effect was seen after long-term (32-week) exposure - short-term (one week) exposure had no effect. Another study reported similar effects of aluminum in triple negative (ER-/PR-/HER2-) breast cancer cells.

Latest review reports antiperspirants should be avoided

The review referenced above was designed to perform a critical examination of current research concerning the links between aluminum and breast cancer risk. Aluminum exposure in daily life is suspected to impact breast cancer development. To conduct the review, the authors searched the PubMed database for relevant terms through November 18, 2022. Cohort studies, case-control studies and meta-analyses all were eligible to be included.
Six studies that focused on the relationship between deodorant and antiperspirant use and breast cancer risk did not produce consistent results. Thirteen studies that attempted to link aluminum content in mammary tissues to breast cancer were also inconsistent — not all of them found higher aluminum content in tumors compared to healthy tissue. However, the authors offer several explanations that could account for the latter findings: (1) an absence of statistical adjustment for breast cancer risks; (2) confusion between deodorants and antiperspirants; (3) failure to assess global aluminum exposure; and (4) a focus on aluminum in mammary tissues when an examination of several metals would have been more appropriate.
In addition, the available clinical studies have been small, retrospective rather than prospective, and were carried out without a long follow-up period. The studies also considered breast cancer as a homogenous disease rather than a heterogeneous illness with various levels of tumor aggressiveness. Importantly, cell studies have demonstrated the carcinogenic potential of aluminum exposure. Deodorants without aluminum are not implicated in breast cancer.
The authors conclude that, based on the precautionary principle and the available data, it is better to avoid aluminum-containing antiperspirants. The precautionary principle allows decision makers to take a cautious stance when scientific evidence about a human health hazard is uncertain and the potential dangers are significant.
Please see our personal care products tag for more information concerning consumer products that could influence breast cancer risk or survival.