Smelly balls

Okayyy so I have a friends with benefits situation with this guy and he likes when I give him head (and he reciprocated) and I love giving him head! The only problem is that his balls smell. So I’m fine sucking his dick but when I go to suck on his balls I gag. How do I bring this up?? I don’t know if it’s something he can help or not, and I dont wanna hurt his feelings, he’s super sweet