I noticed what may be a spider or other insect bite on my upper inner thigh. I can't tell if there are fang marks but there is definitely some skin penetration, a puffed up welt that looks dark purple. The surrounding area is red and there is a red line running horizontally from the inflamed site to the top of my inner thigh. It has hurt all day due to pants friction. What could this be? I am 36, 5'9" and don't have any known allergies.