Redness around Pubic Hair Region

[buterbaugh3]

I have recently developed a rash in the region of my pubic hair.  It started out small and spread throughout the rest of the pubic hair region, which is the only place that it is present.  It is not on my penis or shaft.  It does not itch or feel uncomfortable whatsoever.  The redness or red spots, whatever this is, are not lumpy or elevated from my skin at all, nor do they appear pussey or sore.  

I have experienced this once before, and coincidentally, each time it seemed to have happened after i went to the tanning salon.  The catch is that I do keep my underwear on in the bed, but it just seems like this is the second time after tanning that the rash came back a a day or two later.  This doesn't happen all the time after tanning as the incidents happened months apart, but it is definitely something that I can remember correlating.   Could it possibly be sun poisoning even though my pubic region was not exposed to the light or does this sound like some sort of STD?