I have discoloration, I do not have PCOS (as far as I know) or insulin resistance nor it is a rash. I do have a skin disease, hidradenitis suppurativa, and that has caused some of the discoloration, but my weight has as well. I've noticed the coloring becoming lighter and you can always try lemons, which are well known for lightening skin.

The skin rubbing against each other, not rash related, can cause the skin to darken like it is "dirty." A rash would be red, depending on the type of rash of course, which would be either yeast or fungal related in most cases.

The darkness under my breasts are much better now that I've lost more weight as well as finding bras that are comfortable and I also use a powder too. ;)

The rest of me...meh, i hope it continues to get better with time! :D I have one area that is really a dark brown, which with my skin tone whoa that is dark.

I've had both acanthosis nigricans and discoloration from yeast rashes. In my case, the yeast rashes were red/pink, and the acanthosis nigicans brown and eventually "velvety." The main difference though is that the yeast rashes were itchy and/or painful, while the acanthosis nigricans wasn't uncomfortable.

My fasting and standing blood sugars always fell in the normal ranges, but when I pointed out the brown discoloration to my doctor, he suspected some type of insulin issue, and ordered more sensitive tests including a glucose-tolerance test (you fast for 12 hours, then go in to the lab and have a blood draw, they give you a sweet drink and then test your blood sugar at intervals. I don't remember how long it took, but I think it was at least 2 or 3 hours in the lab).

It turns out that I did have blood sugar issues, but the standard tests weren't sensitive enough to find it. Insulin resistance, metabolic syndrome, Syndrome X, pre-diabetes, it can go by several names, apparently (there's some distinction between them, but a lot of overlap as well).

I also went to a dermatologist for an unrelated skin issue, which the dermatologist suspected was seborrheic dermatitis caused by the same yeast that causes most dandruff. She recommended that I use a dandruff shampoo containing zinc pyrithione (such as some of the Head and Shoulder's products - I usually use Walmart's or Walgreen's store brand equivalent), as a body wash, face wash AND shampoo.

The shampoo not only cleared up the rash, it also cleared up my other skin issues, including the skin-fold yeast rashes. The zinc kills or prevents overgrowth of bacteria, viruses, and yeasts. I hardly ever even get the odd pimple anymore. It even cleared up my itchy feet (which means I may have had athlete's foot, even though my feet looked normal). I use a zinc-oxide cream in addition to the shampoo any time I seem to be getting a flare-up of any skin irritation (My favorite is Johnson's 3in1 diaper rash cream - it's creamy and lotion-like, unlike the zinc oxide creams found in other diaper rash creams or in the sun-screen creams, which are very greasy).

I swear by the zinc pyrithione shampoos - I don't use any other soap. So you could give that a try. Head & Shoulders has several scents, but it's twice the price of Walmart's version (and I like it's scent better than most of the H&S products). You just have to make sure it contains the zinc, because some dandruff products contain selenium or other ingredients.

I prefer the 2in1 (shampoo and conditioner), not only to condition my hair, but because it acts as a face and body moisturizer/ lotion.

I had the discoloration under my arms, mine was related to insulin resistance, in my case, the skin was discolored due to increased circulating insulin in the body, as it deposits throughout tissue it can cause discoloration, i started taking metformin which helped, although i couldn't tolerate the medicine, ultimately for me, weight loss is just as beneficial...so im glad i found 3fc!

I also have discoloration of my skin, under the breasts and inner thighs plus my stomach flap. It's embarassing, but I can rememeber, even as a child, I had those dark areas. I am using metformin and spironolactone for the pcos.