I see I am not alone. The left pit mostly, get soar to the touch on the inside by my chest , it tends to be soar for a day or two then gets a rash. It can get a lump, sometimes it happens on both sides. I can get to a point were every time I move my are it hurts. It hurts right now and is a little red but no Rash. I stopped using all deodorants years ago for this and have not had a problem but the pain and rash returned a few weeks ago, i thought it was a new shampoo so I changed brands again. It just came back yesterday.