I had a friend that had this. He said he was diagnosed with halitosis and actually his dentist helped him get rid of it. He said that he had some stones that had formed in his posterior pharynx, which apparently is an issue that can happen because of excess calcium in saliva. He said because the stones are kinda lodged there, they start to develop a smell after awhile but he got them removed and it was a day and night difference. (we used to be able to smell his breath about 2-3 feet away but after he got treatment, it was completely gone)