Causes leading to breathing through the mouth
Nasal congestion is a common reason why you breathe through your mouth.
You can get allergic nasal congestion, tumors, nasal polyps – are soft, painless, non-cancerous masses, formed as a result of a long-term inflammatory process of the nasal mucosa of the sinuses, which appear in those upper sinuses that drain to the nose.
In addition, other conditions such as sleep apnea can cause breathing through your mouth when you sleep.
When an attack of sleep apnea occurs, you will stop breathing.