Use hydrocortisone twice a day for a week. You can't spread it, scratching leads to scars though. Can't infect other people, etc. If its on face between fingers/toes on your nuts, a doc may give you low dose systemic steroids like prednisone. Benadryl helps with itch, but makes you sleepy.
Goes away depending on sensitivity of skin. Hopefully under two weeks. Warm water helps. Also some kind of bath that helps, ill get back to you.
I'm working in pediatrics now, see it a decent amount