What causes coughing up phlegm?
There are several health conditions — ranging from mild to severe — that can result in coughing up phlegm, including:
Infections.
Allergies.
Asthma.
GERD (chronic acid reflux).
Lung diseases, such as COPD.
Certain environmental and lifestyle factors can contribute to coughing up phlegm, too, including:
Smoking.
Drinking beverages that contain caffeine or alcohol.
Dehydration.
Spending time in a dry environment.