First I want to say my english is not fluent.
Allergic Post nazal drip also makes bad breath. If you have a problem like this, you can use black seed oil. You have to use it during 30-40 days. One drop into each nose hole every day. It can burn. Black seed oil can be taken from mouth as well. If you have intestine or stomach problems, It may help for them too. 1 teaspoon black seed oil everyday. This oil kills all bacterias, microbes or fungal infectios.
I hope it works..