If you want to reassure someone that something isn't harmful or likely to cause injury, call it innocuous. Even an innocuous letter from your boyfriend is embarrassing if your parents find it!
The adjective, innocuous, does not really say what something is, but rather what it is not. Some chemicals, viruses, snakes or websites may be harmful, some remarks or questions may be offensive, but if one of these is innocuous, it is not. The word comes from the Latin roots in- "not" and nocere "to injure, harm."
