What Causes Irritation On The Vaginal Opening?

thank you. i have this tiny irritation just on the soft skin just outside the opening of my vagina. it's not itchy..it's just very irritated. my doctor gave me ratio-amcinonide. that was a month ago. it went away after about a week, and now it's back. he never actually told me what it was..just said these things happen. can you tell me what it is? and should i use this medication again? and also...can i pass this to my boyfriend if we have sex (oral or otherwise)? thanks again. frustrated.