[ceejayoz]

I've only seen people concerned with it in antiperspirants, where it's a salt. (And to be clear, I think it's BS.)

As with NaCl, it's at least possible that the salt and the pure-ish variant aren't quite the same thing.

[wyrdcurt]

Probably not complete BS. This is anecdotal, but years of experience has taught me that aluminum-containing antiperspirants cause contact dermatitis for me after extended use.

I was also diagnosed with a nickel allergy by a dermatologist when I was a child. Metal allergies are real.

I wouldn't go so far as to say aluminum is toxic for everyone, but it's certainly something I avoid putting on my skin.