I noticed a burning sensation and irritation on my right underarms yesterday. My underarms always look darker and have pigmentation since I shave the area often.  No waxing and I always shave. The last time I shaved was 3 weeks ago.   I noticed this irritation and been trying to air out the area as much as possible. The skin feels like burning when the arm is closed.  I tried applying Vaseline and aquaphour gel. It didn't help and the irritation continues. What could be the issue? What does it look like?