Experts at one of the country’s leading cancer hospitals suggest damage caused to skin by shaving the armpits and blocking pores by using deodorant could be to blame for some cases of the disease.
It also names cleavage-enhancing bras as a potential cause, due to the constricting effect of inbuilt wiring on breast tissue and the lymphatic system.
Breast cancer is the most common form of cancer in women in the UK, and more than 4,500 new cases are diagnosed in Scotland every year. About 1,000 Scots die from it annually.
Research carried out at the Western General Hospital in Edinburgh shows not only have cases of the disease increased, but there has been a marked shift in the location of tumours.
After comparing more than 2,500 cases of the cancer in women diagnosed 40 years apart, the team found a “significant” rise in the incidence of tumours in the outer edge of the breast, nearest the armpit. Breast surgeon Dr Adil al-Ajmi, who led the research, said: “Breast cancer is increasing worldwide and cases of cancer and other breast diseases in the upper outer quadrant, which is between the armpit and the breast, are rising.
“We looked at two groups of women who had cancer three decades apart and we noticed that these cases in the upper outer quadrant were increasing, so we looked at the reasons why.”
The paper, which analysed the records of Scottish women diagnosed in 1957-1959 and 1997-1999, suggests “repetitive trauma” to the armpit area could be triggering the formation of tumours.
It states that blocked sweat ducts and skin damage caused by anti-perspirants and shaving can lead to blocked ducts in the breast and the formation of cysts, which have been linked to an increased chance of cancer developing.
The researchers are calling for further investigations to be carried out urgently, but said a number of factors could be to blame.
Dr Ajmi said: “One explanation is that there is a higher amount of breast tissue in this area but this does not explain why the trend has changed over time, so we looked at other reasons. Forty years ago, women were less likely to shave their armpits every day and now this is more common. In the past, they were not using as much deodorant or anti-perspirant.
“We do not want to cause alarm or panic. This could be a difference in lifestyle. But scientists need to do further research. Cases are increasing and we need to know why.”
The paper also suggests some chemicals and additives, such as parabens and aluminium salts used in cosmetics, may be harmful because they mimic the actions of the hormone oestrogen, which is a driver in the most common cases of the cancer.
Jessica Kirby, senior health information manager for the charity Cancer Research UK, warned against jumping to conclusions.
She said: “Any changes that are seen could be influenced by a number of different factors.
“Still, even if tumour location has changed since the 1950s, there’s no evidence at all that it’s linked to the use of personal grooming products, wearing a bra or shaving, all of which were activities that women were doing in the 1950s as well as now.
“The best ways to reduce the risk of developing breast cancer are keeping to a healthy weight, being physically active and cutting down on the booze.”
The paper was published in the online journal of the European Institute of Oncology.