Medication can cause your mouth to become dry overnight, worsening your halitosis. That’s why elderly people, who are often on many medications, are known to frequently find their breath more unpleasant in the morning.
Smokers also may find they have bad morning breath. Smoking not only causes your saliva — your natural mouth rinse — to dry up but also can raise the temperature of your mouth, making it a breeding ground for that dreaded bacteria that causes bad breath. Add this to your list of reasons to quit smoking.
Allergies are also known to lead to bad breath. The mucus that drips down the back of your throat becomes a food source for bacteria. Should your postnasal drip become infected, it can put more odour-causing bacteria in your mouth.