Seeking advice for sensitive underarms (itching and irritation)

Hi everyone, I’m new to Reddit and I’m hoping to get some advice.

I’ve been experiencing itching and irritation in my underarms whenever I use deodorant or similar products. I’ve tried different brands, but most of them seem to cause discomfort. I’ve also noticed some dark spots developing over time.

I’m not sure if this is sensitivity, an allergy, or something else, so I would really appreciate any advice or product recommendations for very sensitive skin.

Thank you so much in advance.