First of all, tell this to them privately. Explain to them that you are telling them, as a friend, that even though they may not realize it, you (and perhaps others) have noticed that they may have an issue with body odor.. . It is very difficult for a person to realize their own faults, problems or annoyances unless it is pointed out to them; if it is done tactfully and gently, your friend may actually appreciate you bringing this to their attention.. . You may want to go the extra step and help them find ways to eliminate the problem. It may be due to poor hygiene or perhaps it could be a medical condition. It's probably not best to jump to conclusions.