What causes excessive mucus? Smoking or exposure to an irritant in the air may cause you to produce more mucus than usual. If the mucus is clear, you might have allergies. Other conditions that could cause excess mucus include bronchitis, chronic obstructive pulmonary disease, and cystic fibrosis. | LifeMoss

The REAL Cause of a Constant Phlegmy (Mucus) Throat

Check out the Mucus Color and it's meaning.