What is lip swelling? Lip swelling is the enlargement or distention of one or both lips due to fluid buildup or inflammation within the lip tissue. Lip swelling may also be referred to as lip edema. A variety of mild to serious disorders, diseases and conditions can lead to lip swelling. Swelling can result from infections, inflammation, trauma or malignancy (cancer). Depending on the cause, lip swelling can be brief and disappear quickly, such as when you have sunburned and chapped lips. Lip swelling that develops over time and occurs along with additional symptoms may be a sign of an infection or extensive inflammation. Because lip swelling and swelling in general may be a sign of a life-threatening condition, such as an anaphylactic reaction, you should seek emergency medical care (call 911) if you experience lip swelling accompanied by difficulty breathing, hives or rash, intense distress, fever, and redness or warmth.