Earlier today my thighs got intensely itchy just out of nowhere, and this lasted for a couple minutes with much scratching. An hour later, I noticed that I had long light reddish purple marks on my thighs (sort of scratch-mark looking), and these marks were dotted with what looked to be bad razor burn, only darker, and the razor-burn like dots only showed up within the scratch marks. What is this, and is it harmful? It's never happened before.