In media stories and on Internet postings some factors have been widely rumored to increase breast cancer risk. For example, right now, there is no evidence to back the claims that antiperspirants, underwire bras, and wearing a bra at night are causes of breast cancer. The claims are based on these concerns:
- Antiperspirant chemicals are absorbed through the skin, block the release of toxins when you sweat, and cause these toxins to build up in the breast.
- Underwire bras cause breast cancer by blocking the drainage of lymph fluid from the bottom of the breast so it can't get back into your body.
There is no scientific evidence to support either of these rumors.
Even the strongest antiperspirant doesn't block all perspiration in the armpit. Most cancer-causing substances are removed by the kidneys and released through urine or processed by the liver. Sweating isn't a significant way for your body to release toxins. And while there are concerns about chemicals, such as phthalates and parabens used for fragrance and preservation, from a whole list of personal care products (including antiperspirants) being absorbed by the body, these chemicals are unlikely to be culprits in causing breast cancer.
Underwire bras do not cause breast cancer. Only one scientific study has looked at the link between wearing a bra and breast cancer. There was no real difference in risk between women who wore a bra and women who didn't wear a bra. Being overweight does increase breast cancer risk though, and women who are overweight are more likely to have larger breasts and wear a bra. Women who don't wear bras are more likely to be at a healthy weight. This difference in weight is probably why this myth continues to circulate.