question: 2 days ago I felt  slightly itchy under one arm.  when I looked, i saw the skin was very dry and dark. Today the skin under both arms is extremely dark and dry, Not where I shave but towards the outter left side.  I have not changed deoderant or detergent.  I did buy a bar of Dove soap for the first time but have only used it twice,  I tried an antibotic cream yesterday, should I continue? I have also been using Castor Oil for the dryness - might that work?