Does stress cause mucus in stool?
Have a cold.
Have irritated sinuses (sinusitis).
Have allergies.
Are exposed to smoke or pollution.
“Environmental allergies can cause excess mucus or phlegm, as can food allergies, but the latter is harder to diagnose based on this symptom alone,” Dr. Bryson explains.
If you’re healthy, your mucus tends to be thin — and you may not even notice it. But if you’re sick, your mucus can become thick and crusty.
And you may not notice phlegm until you cough it up, which can be a symptom of pneumonia or bronchitis.
You may be concerned about the color of your mucus and phlegm, too, whether it’s yellow or green. But the color doesn’t necessarily mean you have an infection.
Phlegm and Mucus: How To Get Rid of It