I once dated a guy with halitosis and had no idea how to tell him that every time I kissed him his breath wreaked!!! I dubbed him halitosis man lol. I eventually had to just tell him straight up after the suggestible mints and gum didn't cover it up well enough. He saw a dentist and found out that he had a bone disease in his jaw and if I hadn't had told him, he might have lost all of his teeth!
Unless this is a high school boy, it's a little scary to think that this guy isn't washing his private areas. None-the-less, you will be doing yourself a favor, or at least the next girl a huge favor by letting him know. Start by making it kind of sly. Let him know that if he wants you to give him oral sex, that you find it sexy if he shaves his whole area and uses some really fresh smelling soap. A lot of times, that works. Tell him if he wants that stuff regularly, to keep it nice and trimmed and smelling good so you can go "down town" if you know what I mean.
If these hints don't work, you may have to all out tell him that his areas smell and aren't groomed to your desire and it makes you not want to do sexual things with him. I'm positive that will do the trick, but best to leave that as a final call.
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