Itching down there after intercourse can be caused by vaginal inflammation, vulvovaginal inflammation or even mycoplasma infection. However, the specific type of vaginal inflammation must be diagnosed by coming to the hospital for a routine leucorrhoea, because there are many kinds of vaginitis, including bacterial vaginitis, mycotic vaginitis and trichomoniasis. If it is not convenient to come to the hospital, you can also use medication empirically. If you are not planning to get pregnant in the near future, you can douche your vagina with cleanser and then use metronidazole vaginal suppositories for 1 week, 1 every night for 7 days. Do not have intercourse during the medication period. Wash your vulva and change your underwear every day, preferably with cotton underwear, not with chemical fiber underwear and not with tight pants. If the symptoms do not improve significantly in a week of continuous use and are getting worse, you must come to the hospital and use the medication under the guidance of a doctor.