Rash on inner thigh? Anyone had this before?

I’ve never posted on here before but thought I might because I definitely need an opinion or something I had this rash appear on my inner thigh after having what I thought was an allergic reaction (my hands and arm got itchy and swollen and now my leg! And I’ve been searching too much and saw something that said it could be something sexually transmitted and a rash caused by that I’m a very paranoid person so my head went right to that any ideas? ~thanks a lot