A study regarding this controversy has been around for years. Although it is an interesting hypothesis, it still remains unproven. You might want to search more on the internet about this. But the main reason for the speculation is that because the natural purging of toxins is empeded by antiperspirants, through sweating, it increases the risk for a person to have cancer.
Here is what National Cancer Institute has to say about the controversy:
However, researchers at the National Cancer Institute (NCI), a part of the National Institutes of Health, are not aware of any conclusive evidence linking the use of underarm antiperspirants or deodorants and the subsequent development of breast cancer. The U.S. Food and Drug Administration (FDA), which regulates food, cosmetics, medicines, and medical devices, also does not have any evidence or research data that ingredients in underarm antiperspirants or deodorants cause cancer.
