Canker sores are painful spots of the inside of the mouth. Canker sores errupt more often on some people more than on others. There has been some anecdotal evidence that licorice 
can soothe and ease the pain of these uncomfortable sores.
Be careful to make sure that you use deglycyrrhizinated licorice, abbreviated as DGL, which appears to soothe muscle membranes. The licorice leaves can be grinded into a very fine form. Mix with a little water and apply it to the sore as needed to provide relief.