I just happened to glance at the back of my deodorant this morning while brushing my teeth, and noticed that it recommended asking a doctor before use if I had kidney disease. Now, I’m no expert on anatomy, but I’m pretty sure that my kidneys are not near my armpits. What gives?
I Googled “deodorant kidney disease” and found this in the first hit:
You can absorb some things through your skin. That’s why they have skin patches for nicotine, pain killers, and birth control hormones. I’m curious what, and how much, gets absorbed from an application of deodorant.
Forget the water supply, comrades. We’ll overthrow the capitalists by putting LSD-25 in their deodorant! 
This seems profoundly silly to me. People with kidney disease can even use foil and cookware.
Not by dissolving it and rubbing it into their skin, they can’t. Foil and cookware are neutral metal, and do not deliver significant amounts of ionic aluminum, whereas antiperspirants are designed to deliver aluminum ions to the skin, and it’s not “profoundly silly” to imagine that the vehicle may even foster transport into the bloodstream. Is the risk from antiperspirants clinically supported? Or even supportable? I don’t know, but I don’t think you can support any argument based on foil and silliness.
See Aluminum Toxicity.
The article has a great deal of medical information on the subject. No mention of deodorants though.
Dammit, so much for my habit of eating a stick of deodorant per day.
It could just be a CYA kind of thing. Because, you know, no one’s ever sued a big corporation for a silly thing like that. 
The foil is supposed to go on your head, not your armpits.
Do you think they don’t know that? They’re quite clever with their mind-control rays.