Cheryl, I have been dealing with the itchy, dark underarms for years...and I recently, within the last year, have found the problem:  itchy, dark underarms are related to insulin resistance.  I obviously have been pre-diabetic for years and years...since childhood.  But no one ever told me, even when I complained about the dark underarms that were driving me to distraction with intense itching!  Last year, I ended up in the ER with terrible pain in my arms/hands. Diabetic neuropathy! Guess what? I didn't know I was diabetic!!  Please go have that sugar checked!  I have to wear braces on my arms and I am in constant pain. I wish someone would have cared enough to treat me years ago before this diabetes damaged my nerves. Good luck. Crystal