Hello, You have not mentioned any present or past history of disease that has affected your lips. Not all creams should be applied on the lips. Efudex treats lesions caused by sun damage apart from pre-cancerous and cancerous skin growths. Do not use on the lips or other mucous membranes. This may cause irritation, inflammation, or absorption into the blood. You are advised to get clinically examined by an ENT, get required tests and investigations done. If you do get the medication in the mouth, rinse with plenty of water. Your treating ENT will give you conservative treatment or recommend other treatment that will be better for you. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K, General & Family Physician