You may have heard rumours that deodorants and antiperspirants could cause breast cancer. But these concerns were started by an e-mail hoax. There is no convincing evidence that antiperspirants and deodorants cause breast cancer.

Why are the claims about deodorants and breast cancer wrong?

The original e-mail claimed that antiperspirants stop your body from sweating out poisons. It suggested that these toxins build up in the lymph glands under the arm and cause breast cancer.

But the details of this are wrong. Breast cancers start in the breast and only later spread to lymph glands. Your body also has several ways of getting rid of toxins, and while sweating is one of them, it is a different system to the lymph glands.

Parabens and breast tumours

Parabens are chemicals found in some deodorants. They are similar to oestrogen, the human hormone that can increase the risk of breast cancer and some other cancers at high levels. But parabens are much weaker than oestrogen itself and any effects are likely to be overwhelmed by natural oestrogen produced in our body, or similar chemicals found in our diet.

A small study found traces of parabens in some breast tumours. Finding parabens in tumours is a far cry from saying that they cause breast cancer. To do that, scientists would need to compare levels in breast tumours to "safe" thresholds, to levels in healthy body cells, or to levels in healthy people without cancer.

In fact, breast tumours have large blood supplies and are likely to contain traces of anything that finds its way into our bloodstream. The study didn’t show that these parabens came from using deodorants rather than intake from food or any other source. And besides, most modern deodorants are parabens-free.

A recent review of the evidence surrounding parabens and breast cancer found that parabens can encourage human breast cells to behave like breast cancer cells, by moving about and invading tissue, avoiding cell death, and suppressing the work of a drug commonly used to treat breast cancer. But there are hundreds of other environmental chemicals that are found in human breast tissue, so it’s hard to be sure that parabens can cause cancer alone.

Aluminium in deodorants

There is no good evidence that aluminium in deodorants could increase the risk of cancer in animals or humans. This was confirmed by a review of all of the available evidence in 2014 that found no link.

A small study in 17 women with breast cancer was quite widely reported in the news in 2007. It found higher levels of aluminium in the part of the breast nearest the skin, and the authors speculated that aluminium in deodorants might cause breast cancer.

But the design of this study was not strong enough to draw that conclusion. For a start, it looked at a very small number of women. And the researchers did not compare levels of aluminium in these women’s breasts to levels in other parts of their bodies, or to levels in women who do not have breast cancer.

Furthermore, a larger study of 176 women in 2013 showed no significant differences in levels of aluminium in normal areas of the breast to the level in the tumour.

So, there is no strong evidence for a link. You can read more about aluminium, deodorants and breast cancer on our Science Update blog (although it’s worth noting that that blog post was written in 2007, so it doesn’t include details of the 2013 study mentioned above).

Some cancer units advise women not to use deodorants containing aluminium salts before going for breast screening. This is not because aluminium salts are dangerous, but because they can obscure the results of screening tests. This can make breast cancers harder to detect.