MedlinePlus Medical Encyclopedia: Fever blisters and canker sores

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Fever blisters and canker sores

Contents of this page:
Illustrations Alternative Names	Information

Illustrations

Canker sore

Fever blister

Alternative Names Return to top

Canker sores and fever blisters

Information Return to top

Question:

Are fever blisters and canker sores the same thing?

Answer:

No. Canker sores occur 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 blisters or cold sores are caused by herpes simplex virus type 1 and are very contagious. Fever blisters often come back in the same location.

Update Date: 5/13/2008

Updated by: Linda Vorvick, MD, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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