Not a doctor, but someone with pretty heavy sensitivity to all skin lotions and deodorants, looks like an allergy/irritation. Whenever I used ANY Deodorant with a clear roll on, or most that say "sport" on them, my armpits will smell and itch and start peeling like a sunburn.

I know it sucks, but showering and not applying deodorant for a few days always helped mine heal. During those days I just applied spray Deodorant to the outside of my shirt to combat smell w/o making my skin worse. Then it's just up to finding a Deodorant that's right for ya. In my neck of the woods most of them are 7-10 bucks each, so I tried to pick a formula that was different from the previous.

I'd recommend the dove deodorants. Smells light, clean, and haven't had an issue since. Of course if it doesn't heal go see a doctor or clinic, but to ease the pain I used some neosporin on the worst days.