I’m intrigued by the story about Mitchum having to recall some batches of their deodorant due to intense irritation affecting users. They have announced that the problem is caused by a change to the manufacturing method. I am at a loss to guess what kind of change that might be. The active in most deodorants is aluminium in various salt forms. Mitchum seems to use two – Aluminum Zirconium Tetrachlorohydrex Gly or Aluminum Chlorohydrate. The pH is quite important in this, but although that might be part of the issue I’d be very surprised indeed if someone had got the pH of the batches in question wrong. It’s about the easiest thing to measure and adjust.