The aluminum concern sounded far fetched, so I did a quick google search and it frequently comes up as myth attributed to conjecture from the 1970s - http://www.alz.org/alzheimers_disease_myths_about_alzheimers.asp.
also this sites talks about it as well - http://www.teenvogue.com/story/deodorant-aluminum-safety-what-you-should-know
That said, it can't hurt to seek out more minimalist natural hygiene products. Frankly they can often just perform better let alone be healthier and cheaper.
Yeah - The concern has been around for quite some time but no link has ever been proven. I've seen truckers with aluminum gear shifting knobs in their trucks suffer from cracked skin on their hands where they're touching the aluminum all day. I personally don't think any metals or their oxides in excessive amounts are good for the body so natural products are sometimes good to seek out.