A fever blister is a sore from an infection caused by the herpes
simplex virus, characterized by an eruption of small and usually
painful blisters on the skin of the lips, mouth, gums, or the skin
around the mouth. A fever blister is highly contagious. A canker
sore is a benign, open sore in the mouth, which appears as a
painful white or yellow sore (ulcer) surrounded by a bright red
area, which is not contagious. A fever blister is very different
from a canker sore, although they both develop in close proximity
in area of the mouth.
Review Date: 02/07/2010
Reviewed By: Linda Vorvick, MD, Medical Director, 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.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
