I think hygiene is really, really important. I could NEVER date someone who doesn’t take care of him/herself this way. I don’t care if a person doesn’t wear perfume or if his/her nails are a bit longer, of if the clothes are a bit creased: cleanness is the important thing.
Maybe he doesn’t realize his lack of hygiene (but I doubt it), anyway you can try help him with “messages” and “signs”. For example, give him soaps and shampoos for his birthday in addiction to some other present. Or… make him come with you at the mall and “accidentally” end up in the personal care area and be enthusiastic in suggesting some product that you find amazing and that he absolutely has to try.
If he’s not dumb he’ll get the message.
If you don’t feel like telling him these things, you can try asking a friend in common (better if it’s a male) to speak with him about this problem. I don’t think you’re the only one disturbed by his behavior.