Depends on the type of dancing. If you are going dancing at a club, then definitely not. If, however, you are going to a hoedown or participating in formal ballroom dance finals, then yes, you need a partner in order to participate effectively.
Ask them nicely to take a bath. If it is in a dance class or P. E. go to the teacher. I once carpooled with a fellow who ate fresh garlic everyday and finally had to ask him to get the pills.