Most commercial antiperspirants contain aluminum in the form of aluminum chlorohydrate. There have been numerous studies on the effect of this chemical on human health. Wikipedia summarizes this succinctly. An excerpt from this
page:
Aluminum toxicity
Aluminum is present most often in antiperspirants in form of
aluminum chlorohydrate.
[25] In addition,
aluminum chlorohydrate[26] is not the same as the compound
aluminum chloride, which has been established as a
neurotoxin.
[27][28][29][30] At high doses, aluminum itself adversely affects the
blood–brain barrier, is capable of causing
DNA damage, and has adverse
epigenetic effects.
[27][31] High doses of aluminum have detrimental effects to a number of species such as non-human
primates,
[32] mice,
[33] rabbits,
[27] and
dogs.
[34]
A preliminary study (2001) showed that the use of aluminum
chlorohydrate, the active ingredient in many antiperspirants, does not
lead to a significant (vs. ingestion via diet) increase in aluminum
levels in the body with one-time use.
[35] The
Food and Drug Administration "acknowledges that small amounts of aluminium can be absorbed from the gastrointestinal tract and through the skin."
[36]
Breast cancer
A 2002 study stated "the rumor that antiperspirant use causes breast
cancer continues to circulate the Internet. Although unfounded, there
have been no published epidemiologic studies to support or refute this
claim."
[37] The
American Cancer Society (ACS) and the
National Cancer Institute (NCI) were very much concerned about the e-mails
rumors directly linking antiperspirants to cancer that both put out information on the
Internet stating there was no evidence linking the cosmetic products with cancer.
[38]
According to the ACS "studies have not shown any direct link between
parabens and any health problems, including breast cancer. What has been
found is that there are many other compounds in the environment that
also mimic naturally produced estrogen."
[39]
According to researchers at the NCI, they "are not aware of any
conclusive evidence linking the use of underarm antiperspirants or
deodorants and the subsequent development of breast cancer."
[40]
"Absence of evidence is not evidence of absence of a harmful effect"
and "these chemicals are being directly applied daily, by very large
numbers of people, and the long-term health effects of exposure are
essentially unknown," toxicologist Philip W. Harvey tells
WebMD in an interview.
[41]
But ACS epidemiologist Michael Thun argued that "even if the parabens
do promote estrogen-dependent tumor growth, the risk from cosmetic use
is "minuscule" compared with other known tumor promoters."
[41]
The cosmetics industry insists the paraben chemicals used as
preservatives in underarm deodorants and other cosmetics, which are
regulatory approved, are safe.
[42]
A 2003 study found a correlation between earlier diagnosis of
breast cancer and antiperspirant/deodorant use.
[43] A 2003 study indicated "underarm shaving with antiperspirant/deodorant use may play a role in breast cancer."
[43]
A 2004 study reviewing the evidence for and against the possible link
between breast cancer and underarm cosmetics wrote "Although animal and
laboratory studies suggest a possible link between certain chemicals
used in underarm cosmetics and breast cancer development, there is no
reliable evidence that underarm cosmetics use increases breast cancer
risk in humans."
[44]
2004 and 2005 studies led by researcher Philippa Darbre, hypothesizes
that particular substances in deodorants, such as preservatives called
parabens, or bolts such as
aluminum chloride used in antiperspirants, get into the
bloodstream or accumulate in breast tissue, where they enhance or emulate the effects of
estrogen, which stimulates the growth of cancerous breast cells.
[45][46]
A 2007 study found that personal care products are a potential
contributor to the body burden of aluminum and newer evidence has linked
breast cancer with aluminum-based antiperspirants.
[7]
A 2008 study stated that no scientific evidence supports the hypothesis
that deodorants and/or antiperspirants increase the incidence of breast
cancer.
[8]
A study published in 2009 by the journal The Breast Cancer Research
proposed a link between breast cancer and the application of cosmetic
chemicals including
phthalates
and aluminum salts in the underarm region, because of their oestrogenic
and/or genotoxic properties, which provides an evidence-based
hypothesis capable of further research.
[47]
Renal dysfunction
The FDA warns "that people with
renal dysfunction
may not be aware that the daily use of antiperspirant drug products
containing aluminium may put them at a higher risk because of exposure
to aluminium in the product."
[36] The agency warns people with renal dysfunction to consult a doctor before using antiperspirants containing aluminum.
[36]
