Bad smell can be because of
1. Poor dental hygiene
2. Nasal discharge and infection
3. Reflux disease and constipation
For poor dental hygiene you must brush daily and keep your mouth clean by doing gargles with Betadine
gargles 2 tsf in half glass of water 2 times a day.
For nasal discharge and nasal crusting you must be aware you have it or not. if yes then take medicines after getting examined by ENT specialist
with nasal normal saline sprays.
If you have reflux then take---
Tab. Mucinac 600 once daily
+Domperidom two times a day half an hour before meals
Syp. antacid gel 2 tsf two times a day half an hour before meals
Keep head end of bed elevated.
Avoid alcohol, Smoking
Do brisk walking daily
Go for walk after dinner
Avoid spicy food
Avoid late night coffee
follow up after 7 days.
and for constipation eat salads and fresh fruits or you can take isabgol husk daily with milk.