http://www.mercola.com/2006/mar/30/antiperspirant_use_increases_breast_cancer_risks.htm
The aluminum salts found in many antiperspirants could increase the risk of breast cancer. Other risk factors, such as shaving the armpits before using antiperspirants, may heighten the risk even further.
Mimics Estrogen
Aluminum salts, which account for 25 percent of the volume of some antiperspirants, can mimic the hormone estrogen. Chemicals that imitate that hormone are known to affect breast cancer risk.
Higher Risk Activities
Given that antiperspirants are used in the armpit, the aluminum salt concentration is highest near the breasts. Applying antiperspirants immediately after shaving will also result in a higher aluminum salt absorption rate due to damaged skin.
Journal of Applied Toxicology February 17, 2006
To avoid all the above harms, purchase Crystal Deoderant instead!
Crystal Deodorant Stick – Regular, 4.2 oz