The Whiteley-Martin Research Centre, Discipline of Surgery; The University of Sydney, Sydney Medical School Nepean, Penrith, New South Wales, Australia. email@example.com
To the Editor:
The effect of deodorant use on breast cancer development has generated considerable interest in both the scientific community and the mainstream media. Primary observational studies and numerous reviews have been undertaken, investigating the effect of regular deodorant use on breast cancer development. To date, the evidence has been largely inconclusive, with evidence of both protective1 and harmful2 effects of deodorant use, whereas other researchers have failed to find an association between the two.3 Although the exact mechanism behind any such relationship has not yet been identified, hypotheses have focused primarily on the anatomical location of the tumors and in vitro evidence of carcinogenesis. Darbre4 found an increasing incidence of tumors in the upper, outer quadrant of the breast and hypothesized that deodorant application to the axilla may contribute.5 The demonstrated estrogenic potential of parabens, a common constituent of deodorant, further supported this hypothesis.5 Alternatively, the increased proportion of breast tissue in the upper, outer quadrant of the breast could explain the higher incidence of breast tumors in this quadrant.6 We reviewed this literature by conducting a database search following the Meta-analysis of Observational Studies in Epidemiology guidelines.7 The databases MEDLINE, EMBASE, PubMed, Current Contents Connect, and Google Scholar (1950–2012) were searched using the search terms “deodorant” AND “breast cancer” OR “breast neoplasm” OR “breast carcinoma.” There was no language restriction, and we did not search for unpublished literature. The inclusion criteria were that a study had an internal control group of women who had not been diagnosed with breast disease and that the study produced a risk estimate. We used a random effects model to calculate a pooled odds ratio for the effect of deodorant on breast cancer. We identified three studies that investigated the effect of regular deodorant use on breast cancer development.1–3 Two met the inclusion criteria. The third study did not include an internal control group2 but rather investigated the effect of antiperspirant use in relation to age at breast cancer diagnosis.
The two studies meeting our criteria were case-control studies that found no increased incidence of breast cancer in regular antiperspirant users. With one1 reporting a markedly reduced risk with regular deodorant use (Fig.). The pooled risk point estimate was in the direction of a protective effect (odds ratio = 0.80; 95% confidence interval = 0.50–1.28; Fig.).
We found no evidence from the combined published studies that deodorant promotes development of breast cancer, despite in vitro evidence supporting the parabens hypothesis.5 One explanation for this discrepancy lies in the pharmacodynamics of parabens and the dosages required to trigger a mutation. While parabens do mimic the activity of estrogen, they lack the potency to cause genetic mutation unless at considerable concentrations.8 The topical application and the low concentration of parabens in deodorant renders the paraben hypothesis less plausible in practice. The lack of primary studies and the quality of the available studies were the main weaknesses of this analysis. With only two primary studies that meet the inclusion criteria, more studies would be necessary to definitively exclude an association between deodorant use and breast cancer.
Prue J. Hardefeldt
Guy D. Eslick
The Whiteley-Martin Research Centre
Discipline of Surgery
The University of Sydney
Sydney Medical School Nepean
Penrith, New South Wales, Australia
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2. McGrath KG. An earlier age of breast cancer diagnosis related to more frequent use of antiperspirants/deodorants and underarm shaving. Eur J Cancer Prev. 2003;12:479–485
3. Mirick DK, Davis S, Thomas DB. Antiperspirant use and the risk of breast cancer. J Natl Cancer Inst. 2002;94:1578–1580
4. Darbre PD. Recorded quadrant incidence of female breast cancer in Great Britain suggests a disproportionate increase in the upper outer quadrant of the breast. Anticancer Res. 2005;25(3c):2543–2550
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7. Stroup DF, Berlin JA, Morton SC, et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA. 2000;283:2008–2012
8. Golden R, Gandy J, Vollmer G. A review of the endocrine activity of parabens and implications for potential risks to human health. Crit Rev Toxicol. 2005;35:435–458