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Is It a Fever Blister or Cold Sore?

By Brock Smith, R.Ph.

Fever blisters and canker sores are two of the most common mouth disorders. They both cause discomfort and cause small blisters in or around the mouth. The fever blister and canker sore are often mistaken for each other.

Canker Sores:

Canker sores occur only inside the mouth, on the tongue and inside lining of the cheeks, lips, and throat. Canker sores occur in about 20% of the population. The sore begins as a small round or oval, reddish swelling. It will usually burst in one day and becomes covered with a thin white or yellow membrane. The sore will usually heal within 2 weeks. Most often individuals will only have a couple of canker sores at a time.

Most people will have their first canker sore between the ages of 10-20 years old. The frequency of canker sores can be from a couple of bouts per year to continuous bouts all year long.

The cause of the canker sore is not well known, it may be from an allergy to a bacterium found in the mouth that may trigger the episodes. In addition, it has been suggested that the sores are caused by a faulty immune system that uses the body’s defenses to attack and destroy the normal cells of the oral mucosa and tongue. British studies have shown that deficiencies in B12, folic acid, and iron may also be causes of the sores. US studies have not confirmed the same findings.

Women are more likely than men to have recurrent canker sores. Female sex hormones apparently play a role in canker sores. Many women have bouts of canker sores only during certain parts of their cycle. Most women experience improvement or remission of their canker sores during pregnancy. Some researchers have used hormone treatment successfully in clinical studies to treat women.

Common treatments for canker sores may include vitamins and mineral supplements, ointments with benzocaine or anti- inflammatory or pain medications. Prescription mouth rinses with tetracycline may be prescribed in more severe cases.

One should avoid foods that scratch the inside of the mouth, use caution when brushing teeth to not irritate the gum or cheeks, and avoid acidic or spicy food.

Canker sores are not contagious.

Fever Blisters:

Fever blisters, also known as cold sores, most often occur outside of the mouth, on the lips, chin, cheeks, or inside the nostrils.

Fever blisters are caused by a contagious virus herpes simplex. There are two types of herpes simplex. Type 1 causes oral herpes, or fever blisters. Type 2 causes genital herpes. Most fever blisters are caused by the Type 1 herpes.

Herpes simplex is highly contagious when the fever blisters are present. Children often get the virus when they are contacted by a parent with active virus or fever blisters. Most people infected with the Type 1 virus more than likely became infected before they were 10 years old.

The virus usually infects the moist membrane of the lips, throat, or mouth. After 3-5 days fluid filled blisters develop and arise on the lips, mouth, or throat. Once a person is infected with the oral herpes the virus remains in a nerve located near the cheek bone. It may stay inactive in the nerve or it may travel down the nerve to the skin surface causing the outbreaks.

Weakened body defenses such as stress, fever, illness, injury, and exposure to sunlight may cause outbreaks of the fever blisters. Like the canker sore they may also have a hormonal link to outbreaks.

Treatment of fever blisters is similar to canker sores. Pain relievers and creams such as Abreva may be helpful. Antibiotics may help with secondary symptoms. Prescription Zovirax (acyclovir) is another treatment option that is available.

What can you do to help prevent fever blisters from occurring? If your fever blisters occur from sun exposure, there is research that has shown sunscreen will prevent the blisters from occurring. Some people believe lysine may help speed recovery time and prevent recurrence of the fever blisters. Lysine is an essential amino acid, which means it is essential to human health, but not manufactured by the body. Lysine is found in foods rich in protein such as: red meat, poultry, pork, certain fish (cod and sardines), cheese (specifically parmesan), nuts, eggs, soybeans, and others. Consult your health provider to find out if your normal diet contains enough lysine. If not, lysine can be found over-the-counter. Typically, lysine is sold in the form L-lysine as tablets, capsules, creams, or liquids. Because of the potential side effects between certain medications and supplements, always consult your pharmacist or physician before adding any new supplements to your regimine.

Researchers are trying to develop a better understanding of how the cold sore and canker sore work in order to develop a vaccine for both.

1. US Department of Health and Human Services
   
2. www.mayoclinic.com
   
3. National Institute of Dental and Craniofacial Research
   
4. National Institute of Health
   
5. University of Maryland Medical Center
   
   
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