Some people report more mucus production after drinking milk and eating spicy foods such as hot peppers, according to WebMD. This is caused by gustatory rhinitis, a reflex reaction triggered by eating food, which results in a runny nose in some people.
Mucus protects the lining of the mouth, nose, sinuses, throat, lungs and gastrointestinal tract, states WebMD. It acts as a protective barrier for the body, preventing the tissues of vital organs from damage. A healthy person produces about 1 to 1 1/2 liters of mucus on a daily basis.
In a study published by the Journal of the American College of Nutrition and posted by the National Institutes of Health, researchers found no link between milk consumption and increased production of mucus. Those who previously believed that milk causes an increase in mucus reported more respiratory symptoms after drinking milk. The study cites investigations that concluded that milk does not seem to exacerbate asthma symptoms.
Milk can cause issues with people with chronic obstructive pulmonary disease, or COPD, due to the effects of the milk breakdown product casomorphin, according to a journal study cited by Everyday Health. Casomorphin is known to increase mucus production in the intestines, which exacerbates the problems associated with the increased mucus production already caused by COPD inflammation. The study states that while there is no clear cause and effect between the increased mucus production in respiratory cells after adding casomorphin, Everyday Health advises the reduction of dairy consumption for COPD sufferers who notice more phlegm after ingesting dairy products.