Trauma of the lip tissues, inflammation or an infection are common causes of lip swelling, according to Healthgrades. Allergies, irritants, injuries and mild conditions, such as sunburn and chapped lips, also are possible causes.
Lip swelling, also called lip edema, is the thickening of one or both lips resulting from fluid accumulation or tissue inflammation, explains Healthgrades. Gradually developing lip swelling with accompanying symptoms, such as warmth around the lips, redness or fever, may indicate a fungal, viral or bacterial infection. Insect bite allergy, hay fever, food allergy and drug allergy commonly involve lip swelling.
Trauma, injuries or irritants that cause lip swelling include lip lacerations, oral surgery, spicy foods, dental appliances and contact dermatitis, says Healthgrades. The swelling also may result from fluid retention, blood transfusion, obesity or lip cancer. People with swollen lips typically experience other symptoms, such as lip color discoloration, blisters, chapped lips or watery eyes.
Lip swelling may be a symptom of an anaphylactic reaction, a life-threatening allergic condition that requires emergency medical care, notes Healthgrades. A patient should get medical attention immediately if the symptoms also include general swelling, fever, tight throat, hives or bluish lips or fingernails. To diagnose the cause of swollen lips, doctors generally ask if the patient has consumed certain foods or has been exposed to unusual substances.