Itchy rash armpit
 

I have a light brown rash in left armpit. It consists of two brown spots--smaller than a dime. It turns a little red at times if I itch it. It doesn't look like much but it sure itches. This has been going on for about three weeks.

Any ideas of what it could be? I thought of allergy but wouldn't that be in both armpits. Also, I thought of seborrhea keratosis AKA seb K. I have many of these on my body. My other seb Ks don't itch as bad.

Last, I thought of fungus. I previously had yeast infection of mouth.

I suffer from PN, but don't think it is relation to this.

Any ideas? Treatments?