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incidence of breast cancer if sufficient of the constituent chemicals were absorbed either from long-term
exposure on the skin (these products are not washed off) or from damaging the skin by shaving prior to
cosmetic application [82,83] . This was proposed partly due to the disproportionately high incidence of breast
cancer in the upper outer quadrant of the breast which is coincidentally also the site of application of
these chemicals. Many years on, it is now known that many of the constituent chemicals can be absorbed
through even intact skin after a single application [84,85] and that they are measurable in human breast tissue
or human milk (see above for references). Published studies have linked the levels of some of these estrogen
disrupting chemicals in the body tissues with personal care product usage [86,87] . However, it is also clear
that these chemicals are getting into many body tissues other than breast and therefore could be expected
to create distant estrogenic microenvironments which could influence not only the growth of the primary
tumour but also growth of metastatic tumours. If excessive use of personal care products is involved in
the development of metastatic breast cancer, then reduction or cessation in use could provide a prevention
strategy.

DECLARATIONS
Authors’ contributions
This review was written solely by the author and reflects the author’s views.

Availability of data and materials
Not applicable.

Financial support and sponsorship
None.

Conflicts of interest
The author declares that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.

Consent for publication
Not applicable.

Copyright
© The Author(s) 2019.

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