Oral lesions make it painful to eat and talk. Two of the most common recurrent oral lesions are fever blisters (also known as cold sores) and canker sores. Though similar, fever blisters and canker sores have important differences.

Fever blisters
Fever blisters are fluid-filled blisters that commonly occur on the lips. They also can occur on the gums and roof of the mouth (hard palate), but this is rare. Fever blisters are usually painful; pain may precede the appearance of the lesion by a few days. The blisters rupture within hours, then crust over, lasting about seven to ten days.

Fever blisters result from a herpes simplex virus that becomes active. This virus is latent (dormant) in afflicted people, but can be activated by conditions such as stress, fever, trauma, hormonal changes, and exposure to sunlight. When lesions reappear, they tend to form in the same location.

Fever blisters can be contagious. The greatest risk of infection occurs during the time when the blister ruptures until the sore is completely healed. The virus can spread to the afflicted person’s eyes and genitalia, as well as to other people.

Treatment consists of coating the lesion with a protective barrier ointment containing an antiviral agent like acyclovir ointment. While there is no cure now, scientists are working on one with the hope that fever blisters will be a curable disorder in the future.

Tips to prevent spreading fever blisters:

• Avoid mucous membrane contact when a lesion is present.
• Do not squeeze, pinch, or pick the blister.
• Wash hands carefully before touching eyes, genital area, or another person.

Canker sores
Canker sores (also called aphthous ulcers) are different than fever blisters. They are small, red or white, shallow ulcers that appear on the tongue, soft palate, or inside the lips and cheeks, but not on the roof of the mouth or the gums. Canker sores usually last five to ten days and are quite painful.

Eighty percent of the U.S. population, mostly women, get canker sores. The best available evidence suggests that canker sores result from an altered local immune response associated with stress, trauma, or irritation. Acidic foods (i.e. tomatoes, citrus fruits, and some nuts) are known to cause irritation in some patients. Canker sores are not contagious because they are not caused by bacteria or viral agents. They cannot be spread locally or to anyone else.

The treatment is directed toward relieving discomfort and guarding against infection. A topical corticosteroid preparation is helpful.
Tips to prevent mouth sores

• Stop smoking.
• Reduce stress.
• Avoid injury to the mouth caused by tooth brushing, hard foods, braces, or dentures.
• Chew slowly.
• Practice good dental hygiene, including regular visits to the dentist.
• Eat a well-balanced diet.
• Identify and eliminate food sensitivities and food allergies.
• Drink plenty of water.
• Avoid very hot food or beverages.
• Follow national guidelines for multivitamin supplementation.

When should a physician be consulted for a mouth sore?
Consider consulting a physician if a mouth sore has not healed within two weeks. Mouth sores present an easy way for germs and viruses to get into the body, making it is easy for infections to develop.

People who consume alcohol, smokers, smokeless tobacco users, chemotherapy or radiation patients, bone marrow or stem cell recipients, or patients with weak immune systems should also consider having regular oral screenings by a physician. The first sign of oral cancer is a mouth sore that does not heal.