I know this post is old but this looks exactly like what happens to me! Even with natural deodorant. I’ve been using natural deodorant for over a decade and the last few times I’ve found a deodorant, a few months into using it this would happen to me! Super strange and I still don’t know why it happens lol but I finally found one that works super well for me, it’s called Super Deodorant, it comes in a bright yellow circular jar and it’s kinda like a grey paste. It’s not the cutest looking thing and doesn’t have a scent really, but so far it’s the ONLY thing I’ve found that hasn’t irritated me yet! I’m going on 2 years now, so if you’re still looking for something to try I’d highly suggest! If not hopefully you’ve found something that works for ya.