In the last year alone, there have been several articles on the subject in the UK and US national press, a refutation by the US Cancer Information Service (http://cis.nci.nih.gov/fact/3_66.htm) and a US study, which found no association between breast cancer and either antiperspirants or deodorants (J Natl Cancer Inst, 2002; 94: 1578-80).

As part of an ongoing population-based, case-controlled study of breast cancer in Washington State, researchers at the Fred Hutchinson Cancer Research Center in Seattle questioned 813 breast cancer patients, aged 20-74, and 793 women without the disease, who all regularly shaved under their arms (so causing nicks and cuts through which potentially harmful substances might be absorbed). They also asked whether the women applied an antiperspirant or deodorant within an hour of shaving.

The patients were less likely than the controls to use antiperspirants (50 vs 56 per cent), and less likely to have done so within an hour of shaving (36 vs 40 per cent). However, they were more likely to have used a deodorant (71 vs 65 per cent) and to have applied it within an hour of shaving.

Nevertheless, one person unlikely to be convinced is Dr Philippa Darbre, a senior lecturer in molecular cell biology at the University of Reading, who has spent 20 years researching the mechanisms of breast cancer cell growth. She points out that the incidence of breast cancer has doubled in the last 20 years in England and Wales alone to nearly 40,000 cases by 2002.

To explain this, Darbre suggests that underarm cosmetics (antiperspirants/deodorants) are involved - not least, she claims, because of the disproportionately high incidence of breast cancer in the upper outer quadrant of the breast, up from 31 per cent in 1926 to 61 per cent in 1994, just the place where these chemicals are applied with ever-increasing frequency. She notes, too, that there is a growing incidence of breast cancer in men, seemingly in line with increased use of these products.

It’s the fact that such products are not rinsed off and are used repeatedly throughout life that causes her alarm. Cancer arises most commonly in the left breast and, she believes, this may be because most of us are righthanded and apply the products more forcefully to the left underarm. There are no label instructions on the safe level of usage nor do we know how safe the chemicals are with prolonged use by prepubertal youngsters (Eur J Cancer Prev, 2001; 10: 389-93; www.campaignfortruth.com/ Eclub/151102/underarmcosmetics.htm).

Dr Darbre was among the supporters of a campaign, run by the Women’s Environmental Network and the Ban Lindane Group, urging the UK government to provide a national prevention strategy for breast cancer, including fostering research into the variety of pollutant chemicals now known to accumulate in human breast fat.

At a meeting with the all-party parliamentary group on breast cancer in 2002 (www.wen.org.uk/health/support statements), Dr Darbre put forward a document showing the increasing evidence that many pollutant chemicals are capable of damaging DNA and mimicking the action of oestrogen. Cancer begins by damaging growth genes in DNA, and about half of all breast cancers are fuelled by oestrogen; indeed, antagonism of oestrogen is the basis of the clinical treatment of breast cancer. Accumulation of oestrogenic chemicals in the breast could therefore potentially influence both the incidence and treatment of breast cancer.

But there are problems in running the studies that are needed. One is the difficulty of taking samples of human breast tissue, particularly from women without breast cancer. Most studies have used milk or blood samples, which may not truly reflect the accumulation of chemicals in fat. Then there is the question of deciding which chemicals to measure - for example, there are some 209 forms of polychlorinated biphenyls, all used as pesticides.

Darbre also worries about parabens, oestrogen mimics that can penetrate the skin and which are used in some deodorants as a preservative. They are generally listed as alkyl parahydroxy benzoates: butyl/methyl/ethyl/propylisobutyl parabens. Cosmetic manufacturers point out that parabens don’t penetrate intact skin, and allergic reactions are rare (www.guardian.co.uk, 25 February 2003).

In fact, many deodorants are paraben-free, relying instead on preservatives such as aluminium or zirconium. These compounds help prevent sweating in antiperspirants, but they may also be cause for concern.

Simple deodorants only intend to mask odour and don’t use such agents. But, according to one chatroom on the Net (www.healthypages.net/forums/topic.asp?TOPIC ID-1625), they’re not that easy to find. People favouring products containing ‘alum’ were horrified to learn that this is another name for aluminium ammonium sulphate.

Dr Darbre’s hypothesis remains controversial, and even she would agree with NHS Direct (www.minervation.com/cancer/breast/patient/what/ common.html) that there is no solid evidence that either deodorants or antiperspirants can cause breast cancer. So, given the unproven issues behind this particular topic, for the moment, there is no second opinion. The only opinion that counts is your own. Deanna Wilson Deanna Wilson is a freelance medical and healthcare journalist based in London.