Halitophobia could develop quite innocently, through a minor breath problem. They try to avoid it and take a mint. Then they want something stronger and start brushing their teeth a lot, but it is never quite enough. The phobia builds up and takes over. For example, they may be rejected by a partner and blame that on the bad breath they think they have.
Life gets miserable and they blame their breath.
Blaming misfortune on bad breath is exactly what Joe Wallace did. He had never been unduly concerned about his breath until an argument with his daughter. But I do remember that she told me not to shout at her because I stank. I was devastated and couldn't understand why no one had ever told me before. I also noticed people watching me on the tube.