system
Given the following post, respond as if you're commenting on Reddit:
human
I got a new deodorant recently that says that it has no aluminum or parabens. Is there research showing that aluminum and parabens are harmful in the quantities that they usually come in in deodorant?

I.e. when you consider the concentration that they're in in deodorant and when you consider that people use a tiny amount of deodorant once or twice a day, are those amounts of aluminum and parabens harmful to humans?

Edit: WOW this blew up while I was at work. Thanks for all the replies, everyone!
gpt
Not so much harmful, but some people have skin reactions to either aluminum or parabens (or both), so there's a market for deodorants/antiperspirants without these additives.  
  
Aluminum is added to some deodorants as an antiperspirant (helps you sweat less).  
  
Parabens are not commonly used, but they help reduce bacterial and fungal growth (on both the body they are applied to and on the deodorant stick itself), which is part of how those products work, since body odor is often the result of surface bacteria byproducts.  Kill the bacteria or fungus, and the odor "problem" is solved.  
  
Neither substance has been shown to be harmful in the amounts encountered in deoderant products.