Smoking habits, dry air in the room, drugs and a number of certain clinical conditions can cause thick phlegm such as jelly, especially if accompanied by changes in sputum color. Check out more in the following review! Phlegm is mucus consisting of proteins, enzymes, and antibodies produced by respiratory organs, namely the lungs and throat. The body produces mucus to protect the respiratory system. You do this by moisturizing, recognizing, capturing, and removing dust and microorganisms, such as bacteria and viruses, from the nose and throat. Thick phlegm like jelly generally occurs when we are sick, or when too many foreign particles enter the inflammation or allergic reaction. Causes of thick phlegm like jelly Spitting phlegm is actually a natural thing to happen. Phlegm removed by coughing, and sometimes accompanied by other symptoms, such as nasal congestion, runny nose, and sore throat. However, if the production of phlegm is too much and thick like jelly, it can clog the ...