What are these dark marks under my arms?

I have dark, dryish marks on my underarms, and I'm not sure where they came from or how to get rid of them...
I thought that maybe it was the dye from my clothes (I wear a lot of black) that got into my skin after I sweat? That or maybe it had something to do with the deoderants/antiperpirants I use, because I heard that antiperspirants just clogs the pores so you don't sweat, and maybe it was from the buildup.

I've tried scrubbing and everything, I've even gone a few days without wearing the antiperspirant or black clothes, but nothing has worked so far.

Does anyone know how I can get rid of it?

Hi,

Are you female? Do you have any other things that seem out-of-whack or strange?

If you are a female, and have these dark patches along with:
- Painful cramping before period
- Skin tags
- Difficulty in losing weight, or excess of gained weight
- Excessive hair

You could have PCOS- or Polycystic Ovarian Syndrome. A close friend of mine has it, it's a hormonal imbalance. The dark patchy spots under the arms are a sign of it.

If you don't have any of those symptoms or if you're a guy, it could be a boil or cyst. Do the marks hurt at all? You could see a dermatologist to be sure.

Good luck.

O MY GOSH! IHAVE THAT TOO! AND I HATE IT! I ALWAYS WEAR LIKE LONG SLEEVED SHIRTS OR AT LEAST NO TANK TOPS BECAUSE THIS ONE TIME WHEN I WAS A KID A FRIEND OF MINE ASKED WHY I HAD DARK PUPLE LIKE ARMPITS! I WAS HORRIFIED BBECAUSE I THOUGHT IT WAS JUST A NORMAL THING, I DON'T KNOW WHAT IT IS... IM 16 BY THE WAY.

I just turned 17, and I am female. I can't really remember when it started to show up, but I don't remember having them before I was 13 or 14...which was around the time I started wearing black (If that even has anything to do with it.)

I thought maybe the dye had something to do with the marks, because I once bought a robe and I wore it after I took a shower, and since it was new, the water on my hair made the dye bleed onto my back..so I was thinking maybe the dye bleeds into my pores when I sweat? And that the dryness might be from my deoderant or something. I'm just not sure if anyone else had heard of this problem or knew how to take care of it.

Thanks for your answers, by the way. They are very helpful. I'm trying to look into this as much as I can.