What Could The Blister In Vagina Be Indicative Of?

Hi, may I answer your health queries right now ? Please type your query here... Once in a while, I would have this blister like swelling around my vagina OR now anus. It goes away without medication BUT it is uncomfortable when I have one. I thought this is caused by shaving the area. I never thought I would have herpes? AND I am NOT sexually active for almost a year now. What is this?