Red, itchy rash on inner thighs ~ any ideas?

Sunday afternoon I had company and put on panties for the first time. Later that night, I noticed a bright red, very itchy rash on both inner thighs...traveling to my buttocks. Called the dr Monday a.m., Monday p.m. and again today, but no reply. The rash has spread slightly. Benadryl takes out the itch. Any ideas?

I went off of the Darvocet Sunday, thinking that was a cause of the rash. Now taking Ibuprofen and that helps.

I had (sort of) similiar situation. Both my thighs were itching like mad. My Dr really didn't know what would cause that but some have suggested it was from anti biotics and other meds. I too, used Benedryl and got some relief from that. Drinks lots of water to help flush any medications out of your body.