With girls the inner lips and vagina are often red, irritated and itchy. You may have a burning sensation when urinating. There may be a watery or thick cottage cheese-type discharge. Intercourse and inserting a tampon are normally painful.
Guys often have no (serious) symptoms. If they do, the glans is often red and flaky. The foreskin and glans can also itch and urination can be painful.
Sometimes it heals by itself. If it’s not gone in a week you should go to your GP to have it checked out. Sometimes you have to try different medicines before it is gone.
When you are treated your partner should be treated as well. Otherwise you run the risk of getting it by turns: the ping-pong effect.