It could be irritation. Blisters could also be infection, but infections wouldn't come and go. An allergy to antiperspirant wouldn't look like this, and would of course affect both sides. I think you should clean the area gently, apply an over-the-counter antibiotic like bacitracin, and see a skin doctor for diagnosis and treatment.
Best.
Dr. Rockoff
I also just found out that my wife started soaking my clothes in oxyclean and tide. The washer does not rinse well. Could the laundry chemicals cause this?
That sounds a little like hidradenitis. Could it be?
I have read other comments regarding underarm itch and nothing is being attributed to deodorant. I have this problem of great itching underarms. It is nearly insatiable once the scratching starts. I never use anti-perspirant,I always use deodorant. I am currently using a roll-on of mineral salts and it seemed to work for a while but now the rash has returned. Is this asymptomatic for many people or am I just an isolated case among a very few...
Thanks for any help
Peter T