These pesky blisters are painful, ugly, and slow to heal. What we call cold sores or fever blisters are caused by the herpes simplex virus. Herpes infections are reoccurring, plaguing us in times of high stress or other illness such as a cold or fever—hence the name. It is said that most of us have acquired this virus by the age of 20.
These blisters are red raised areas filled with fluid. Several small blisters often merge to form a larger one. They appear on the lips, the roof of the mouth, in the nose, or on the face. Once they rupture, bright red skin is exposed that scabs over.
Canker sores form on the tongue, the gums, and the inner sides and the base of the mouth. They appear as white or yellow blisters circled in red. These sores are actually ulcers, small bacterial infections. They can be caused by irritation or injury to the mouth from orthodontia, sharp foods, or rough toothbrushes; by food allergies; or from vitamin deficiencies such as iron, folate, or vitamin C or vitamin B12.
Both infections may include swollen lymph nodes and flu like symptoms.