There are a bunch of diseases associated with these darkened areas, but it’s one of those things where it’s either going to be diabetes type 2 or you can look it up, now that you know what it’s called (or at least where to go to find out again).  It’s also found in the groin and belly button region.

Ps. The armpit is sometimes referred to as the axilla by people who like to make life hard by using fancy-pants terminology.

This is, I believe, my fourth diabetes comic, but it’s pretty cool that you could very well diagnosis someone with diabetes type 2 by having read this comic.  It’s especially cool since diabetes is not something you want to ignore/be oblivious to, so you’d be doing them a huge favor.