Swollen lips. What you are able to use to treat a swollen lip, depends on the cause of the swelling, and what part of the lip is swollen. If the swelling is due to an injury (being hit) then a cold compress is best. Infection, will require attention and antiviral or antibiotic as needed. Allergic reaction to food, medication, or an object touching the lips may also cause swelling. Antihistamines will help this.