What Causes Itchy Rashes And Swelling On Thighs?

33. 5'2''. 224. Female. I have a rash on the exterior of both thighs that is swelling and very itchy. The inital place of where I noticed the first rash is warm to touch. I am assuming it is poison ivy because I am very allergic, and seem to get it at this time every year. However, I can not recall being around the woods. We were at the lake all weekened and this rash began the Monday/Tuesday after we returned.