hi this could be from the mucus inside her vagina i would suggest that she has a simple test done at her doctors could be that its high in acid. hence you get a rash. do hope this helps. good luck
small red whelp like bumps and red dots appear on penis after unpretected sex and the next intercourse it itches? . in a relationship with the same girl for over a year now. first 6 to 8 months never used a condom as she is on bc and never had a single issue but the last 3 months every time we have unprotected sex my penis gets irritated with red whelps and bumps. then the next sessions it feels like i am scratching an itch and i climax quickly. days after it will dry up and disappear. tried using a condom for a month and when we stopped it happened again. she has absolutely no symptoms or signs at all.