propanediol vs propylene glycol

Propanediol versus Propylene Glycol - explains the difference.

Some years ago when several deodorants started listing propanediol in their ingredient list, I looked up what it was. Based on the info I found, I thought it was just another name for propylene glycol.

Seeing as some personal care products stated on the label that they were propylene-glycol-free, yet they had propanediol in the ingredient list, that seemed deceptive to me. Or as some kind of marketing ploy - apparently some people are allergic or sensitive to propylene glycol, or dislike it for other reasons. I've never noticed any problems with it, personally.

But the document at the above link explains that both compounds really are very different, even though they have the same formula, C3H8O2.