What is meant by the sudden swelling of the upper lip?

Sudden swelling of the lips is a common symptom of angioedema, an allergic reaction that is believed to be triggered by eating shellfish, exposure to animal dander and ingestion of certain medications, according to MedlinePlus. Angioedema sometimes accompanies medical conditions such as lupus and lymphoma.

Severe allergic reactions to bee stings can also cause rapid swelling of the lips, according to WebMD. The condition is referred to as anaphylactic shock, and additional symptoms can include nausea, vertigo, swelling of the tongue or throat, and loss of consciousness. It is important for individuals experiencing potential signs of anaphylactic shock to seek immediate medical attention.