I tend to wear a lot of white t-shirts to work either under jackets, vests, etc, so I have quite a few. All of a sudden, about mid-summer, I started noticing that all of my white t's were getting these weird stains down the front or the back of them. The patterns were the same, but it wasn't always in the same place. I didn't notice it until they came out of the wash, so I was ready to blame the wash (and I started wearing colored t's).

Just last night as I was lying in bed trying to fall asleep, I was going over all the things in my bag for my ride after work today. We go for sushi (or some other food) right after riding, so I always want to make sure I have something somewhat suitable to wear. Baseball hat? Check. Non-cycling shoes? Check. Towel to wipe off my face? Nah...I'll just use my t-shirt again.... LIGHTBULB !!

Holy cow...I have been ruining my white t-shirts by using them to wipe the sweat off my face after riding. I wear a light mineral makeup to work and apparently when you mix it with sweat, it stains cotton. Duh! Mystery solved!!