The chemicals were found in breast cancer tumours
Chemicals from underarm deodorants and other cosmetics can build up inside the body, according to a study.
British researchers have found traces of chemicals called parabens in tissue taken from women with breast cancer.
While there is no evidence they cause cancer, the scientists have called for the use of parabens to be reviewed.
The cosmetics industry insists the chemicals, which are used as preservatives and are approved for use by regulators, are safe.
Dr Philippa Darbre and colleagues at the University of Reading carried out tests on samples of 20 different human breast tumours.
Writing in the Journal of Applied Toxicology, they say they found traces of parabens in every sample.
Their tests suggested the chemicals had seeped into the tissue after being applied to the skin.
"This is the first study to show their accumulation in human tissues," said Dr Darbre.
"It demonstrates that if people are exposed to these chemicals, then the chemicals will accumulate in their bodies."
Dr Darbre said there may be reason for people to be concerned about the findings.
"Their detection in human breast tumours is of concern since parabens have been shown to be able to mimic the action of the female hormone oestrogen," she said.
"Oestrogen can drive the growth of human breast tumours. It would therefore seem especially prudent to consider whether parabens should continue to be used in such a wide range of cosmetics applied to the breast area including deodorants."
Dr Philip Harvey, European editor of the journal, said the findings should be interpreted cautiously.
"Further work is required to examine any association between oestrogenic and other chemicals in underarm cosmetics and breast cancer."
Chris Flower, director general of the UK's Cosmetic Toiletry & Perfumery Association, welcomed the study.
"It is welcome additional information and we will want to examine the findings in detail," he told BBC News Online.
"However, parabens have a very, very good safety profile. We have an enormous amount of information which supports the safety of these chemicals and their use in cosmetics."
Delyth Morgan of Breakthrough Breast Cancer said: "This extremely small study does not demonstrate a direct causal link between deodorant or antiperspirant use and developing breast cancer.
"Further research is needed to establish the source of the chemicals found in the breast tumour samples and what, if any, the relationship is to breast cancer."
A spokesman for the UK's Department of Trade and Industry said government scientists would examine the findings.
"Parabens are approved for use in the UK and in Europe and all the information we have suggests they are safe to use.
"However, British scientists will examine this study."
Dr Richard Sullivan, head of clinical programmes at Cancer Research UK, said there was no evidence that deodorants were linked to an increased risk of breast cancer.
He said the latest study was very small, and had by no means produced conclusive results.
"The increased incidence we are seeing of breast cancer can be explained by many other factors," he said.