Tinea Versicolor?

[Bowater]

I currently have a big brown spot on my arm that starts under the armpit and moves around by bicep.  I was told it was Tinea Versicolor because of the amount of sweat I endure from sports.  However, I applied Selsun Blue and it stung like crazy, but did not disappear.  When I apply Selsun Blue now, it doesnt sting anymore, but it is not removing the spot.  This spot is smooth and for the most part is in tact.  However there are a few outlier spots close to the main spot.  I have had it for 3-4 years and a medical doctor thought it was a birthmark.   I dont remember being born with it and I dont think a birthmark should have a reaction to Selsun Blue like it did.  Any advise on what this spot might be and how I might go about getting it fixed.  

[Vanessa Lacuesta]

Hi

You have been having this for the past 3 years (is this correct?) and during that time, there is no change in the character of this spot?

How did this start?

This may not be a fungal infection. This appears to be hyperpigmented skin, however the cause at this point is not known. This may be a birthmark as its description closely resembles your case. If this does not give your any form of discomfort, then this may not necessarily need any intervention.

[Bowater]

I first noticed it my sophmore year in college.  It has grown in size, but has stopped or slowed down to wear I cant tell any additional growth.  It started under my armpit and moved around to the outer part of my bicep.  It completely covers my bicep now.  When I flex my muscle, the spot perfectly covers the muscle.  I worked on a golf course one summer and sweated continuously, I was thinking that I got some sort of fungus from that.  I have a single white dot at the very top of the spot, which makes me think its some sort of pigment.  I obviously dont know what Im talking about :).  It is smooth and tan.  It gets darker with sun.  The selsun blue made it lighter.  It had a chemical reaction and a layer peeled off making it lighter. Does this help?