I would try liver and bowel cleanses. They're easy, cheap and fast and can help cure a myriad of problems. Does he have a lot of fillings? If so you might want to look into getting those out. Check the Amalgam Forum for more info.
Good luck. My nephew has cystic Acne and it's very stubborn. Although, he's young, eats a horrible diet and refuses to do any cleansing so hopefully your hubby will have better luck :)