Breast cancer patients who apply moisturizers may be dosing themselves with estrogen without even knowing it, investigators reported at a breast cancer symposium in San Antonio.

Dr. Adrienne Olson, with Breastlink in Hawthorne, California, and colleagues analyzed 16 widely available moisturizers for estrogen-like compounds.

None of the creams analyzed noted any estrogen content in their list of ingredients. Even so, six samples contained estriol or estrone.

Olson, who is a seven-year breast cancer survivor, explained that estrogens applied to the skin are more efficiently absorbed into the body than estrogens taken orally.

She urged women with breast cancer that is driven by estrogen (that is, estrogen-receptor positive breast cancer) to avoid externally applied estrogen to minimize the risk of a recurrence.

Women without breast cancer are also at risk, she added. If they use estrogen-containing topical moisturizers, they may be dosing themselves daily with estrogen for extended periods, thereby boosting their risk of breast cancer.