According to the American Cancer Society, there are no strong studies in medical literature that link breast cancer risk and antiperspirant use; however, it's definitely a concern, especially among the breast cancer community.
Before I continue sniffing into this topic, let me explain difference between antiperspirant and deodorant. Antiperspirant keeps you from sweating while deodorant cut down on what makes you smell when you do sweat.
Why is this a concern? Antiperspirants do their job clogging and blocking your sweat pores with aluminum salts. Some research suggests that when aluminum is absorbed by the skin, it can cause changes to estrogen receptors of breast cells. Because estrogen can promote the growth of cancer breast cells, some scientists have suggested that the aluminum-based compounds may be a risk factor for the development of breast cancer.
Finding the right Deodorant/Antiperspirant has been quite the challenge for me. I've tested many and some worked initially, but later became what I thought was a stinky purchase.
I finally stumbled on a brand called UNDERARMED on Amazon. It had a close to 5 star rating and reviews seemed far from unauthentic. After researching, I found that UNDERARMED was created by small family business (started by Sean McLellan). They hand make each stick and took over two years and over 200 attempts to formulate the perfect product! Ingredients are limited (that's usually a good sign) and include natural stuff like organic coconut oil, beeswax, all natural aluminum free sodium bicarbonate, organic avocado butter and a few more they list in the packaging.
How did they get it right? Sean isn't a scholarly chemist nor did he go to the Harvard of Deodorant School. He simply did this by asking all his purchasers to send him feedback after using. As a gift for the information, he provides a trial size deodorant for $1 (the small payment is to help with the cost of shipping). Today, after all his trial and error, he says it's finally perfect! And so far, I think it is too.