Alternative NamesCanker sores and fever blistersInformationQuestion:Are fever blisters and canker sores the same thing?Answer:No. Canker soresoccur only inside the mouth and are not contagious. They sometimes occur as a result of trauma (biting the inside of the lip, burning the mouth with hot food), but may also occur without any known reason.Fever blistersor cold sores are caused by herpes simplex virus type 1 and are very contagious. Fever blisters often come back in the same location.ReferencesGonsalves WC, Chi AC, Neville BW. Common oral lesions. Part I. Superficial mucosal lesions. Am Fam Physician. 2007;75(4):501-507.Habif TP. Warts, herpes simplex, and other viral infections. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009: chap 12.