Aluminum-free deoderant - should I be worried about aluminum?

I've always been a little confused about the presence or absence of aluminum (see, I spelled it the North American way - I'm practically a local now!) in deoderant and antiperspirant. 

Pretty much all deoderants these days boldly advertise "aluminum-free" or "0% aluminum". So, I naively assumed, probably like most other people, that aluminum on the skin is bad for you. After all, too much aluminum in the brain can cause dementia, can't it? Gruesome animal experiments have proved that.

However, I recently read an article referring to the aluminum-free trend as a "marketing scam", so I looked into it. Well, it seems that aluminum blocks the pores and so prevents sweating from the area of skin it covers (known since the late 1800s), which is why it is an essential ingredient in antiperspirants. Antiperspirants are designed to stop underarm sweating because it is unladylike and antisocial to smell of sweat (and, let's face it, these things are mainly marketed to women).

So, antiperspirants, by definition, contain aluminum. Deoderants, on the other hand, which seek only to mask underarm sweat smells and not to stop sweating completely, by definition, do not contain aluminum. So, advertising "0% aluminum" on a deoderant is technically correct but unnecessary and redundant, similar to advertising fat-free popsicles or gluten-free vegetables. In that respect at least, it is a marketing scam.

But there is still a lot of confusion out there about the aluminum in antiperspirants. Antiperspirants (containing aluminum) are still sold, they're just a bit misunderstood and face a lot of public disapproval. This is largely due to one of those well-meaning but ill-informed viral scare campaigns that do the rounds of the internet from time to time, claiming that antiperspirant is the leading cause of breast cancer, and that it occurs because antiperspirants block sweating, the body's natural means of purging toxins, and that they somehow cause DNA damage leading to cancer. (It doesn't, take the American Cancer Society's word for it.)

The Slate article humorously enjoins us to maybe not inject aluminum directly into our brains, just in case, but that's about the size of it.