Quote Originally Posted by ny biker View Post
I am the queen of contact dermatitis so a reaction to the elastic could also be an issue. One more thing to think about...
I have some kind of a reaction under my sports bra and my socks, only after long runs in warmer weather (3+ hours). Large dark pink blotches, raised little to not at all, doesn't itch - I wouldn't even know they were there except for catching them in the mirror or my DH's eyes.

I think it's a combined reaction to detergent residue plus slight movement under a tight garment and/or lack of wind cooling/evaporation, since it doesn't happen on the bike no matter how long I ride or how much I sweat.