A canker sore on the lip is among the most painful mouth canker sores.
A canker sore on a lip can be located on the mucous membrane of the lips. You CANNOT get a canker sore on the outside skin of the lips beyond the vermillion border. If you have a sore on this part of the lips it is not a canker sore as canker sores are always on the mucous membrane of the lips.
Canker sores on the lips can be very painful because the lips are sensitive. Canker sores located on the lips can be easily bitten (ouuuuuuuch!) which makes them difficult to heal.
If you often have canker sores on the lips, AftaZen is a preventive treatment that can keep them away from your lips. Learn how: