I have dark underarmdar can you help me with that?

Skin color changes..: If I understood well you have dark skin change under your arms. One possibility is a fungal infection so Lotrimin (clotrimazole) or Nystatin over the counter can help. It could also be changes associated with insulin resistance especially if you are over weight. In other words this could mean you might be at risk of having diabetes at some point. A final diagnosis should be made by an exam so make a vsit to PCP.