Cold Sores and Canker Sores?What Is the Difference?

NOVEMBER 01, 2004
Barbara Sax

Cold sores and canker sores are 2 of the most unwelcome oral problems patients can develop. Whereas the 2 conditions occur on or in the mouth and patients often confuse them, their causes are very different. These common lesions may not be dangerous, but they are painful and unsightly, so pharmacists are likely to field plenty of questions from patients desperate for treatment.

Cold Sores

Brad Rodd, DDS, professor at the University of Alabama in Birmingham, estimates that 20% to 30% of people suffer from recurring cold sores (or fever blisters), which are caused by the herpes simplex type 1 virus. Like its cousin the herpes simplex type 2 virus, which causes genital lesions, the virus that causes cold sores is contagious.

"Most people come into contact with the virus when they are children," Dr. Rodd said. "In some cases, the virus sets up shop in a nerve ganglion in the body. While it doesn't affect the nerve, it can exist in the nerve forever and can erupt to the surface from time to time when a patient has a cold or fever, is experiencing stress, is exposed to the sun, or when there's trauma or stress to the area, such as a patient might experience on a visit to the dentist."

When conditions are ripe, the virus can come "marching out," said Dr. Rodd, resulting in a painful and unsightly eruption on the skin. Lesions first become visible as small, red papules or fluid-containing vesicles about 1 to 3 mm in diameter. Many lesions can coalesce into a single larger lesion, and, as the sore matures, a crust forms over the vesicles that have erupted. Cold sores usually are self-limiting and generally heal without scarring in 7 to 10 days. "Cold sores aren't so much painful as they are embarrassing," he said.

Unfortunately, there is not much that patients can do to prevent the virus, and, once contracted, the virus cannot be eradicated. "These viruses are hidden deeply in the body so that drugs can't reach them, so there's really no cure," Dr. Rodd said.

The promising news, according to Dr. Rodd, is that, if patients treat the outbreak quickly enough, they can beat the sore back before it gets too "comfortable" on the skin's surface. "Patients should treat the area as soon as possible?the very second they feel something coming on," he said. Because lesions tend to form in the same spot, patients usually can tell when an eruption is about to occur, due to tingling, burning, itching, or numbness in the area.

Dr. Rodd recommends either Abreva or the Zilactin line of oral health care products, OTC products that he believes can effectively inhibit the development of cold sores. The active ingredients in these products (doconasol in Abreva and benzyl alcohol in the Zilactin products) suppress sensory receptors and offer relief from pain and itching. Anbesol, Blistex, Campho- Phenique, Carmex, Orabase, and Orajel are other products recommended by pharmacists for treating cold sores.

Dr. Rodd cautions that highly astringent products containing ingredients such as tannic acid and zinc sulfate are not safe or effective treatments for cold sores and should be avoided.

Pharmacists also can recommend that patients keep the area moist as the lesion begins to form a crust. If the lesion cracks, it may be more susceptible to secondary bacterial infection, which can delay healing. Common skin protectants, such as petrolatum and cocoa butter, can be used to keep the area moist.

Patients who have recurring, but not debilitating, cold sores may want to consider a more systemic approach. "There are a lot of medicines that can treat symptoms, but it may be a good idea to try to prevent cold sore episodes," said Tony Welder, owner of Dakota Pharmacy in Bismarck, ND. "There are many natural medicines that can strengthen the immune system. Many people benefit from lysine or balanced amino acids as a preventative, besides strengthening the immune system with essential fatty acids and vitamin C. The treatment of cold and canker sores with probiotics or enterobiotics may seem strange, but it works." Many pharmacists recommend Herpecin-L, a product that contains lysine, an amino acid thought to interfere with the ability of the herpes virus to absorb arginine (necessary for its reproduction).

Canker Sores

In addition, Welder suggests a boost to the immune system as a prevention against mouth sores or canker sores. Also referred to as recurrent aphthous ulcers, canker sores are found exclusively inside the mouth. They can range in severity from ones that occur occasionally and are self-healing to very large and numerous ulcers that can be difficult to heal.

The sores usually form on the tongue, the floor of the mouth, the soft palate, or the inside lining of the lips and cheeks. Most lesions last 7 to 14 days and heal spontaneously without scarring.

Whereas cold sores have a known cause, the cause of mouth sores remains elusive. "No one knows why they occur," Dr. Rodd said. "We know it's not an infection. It's probably some sort of localized inflammation problem. There are fairly complex interactions going on at the ulcer level, but we really don't know much more."

"When mouth ulcers are large, numerous, and difficult to heal, they can be debilitating for a patient," said Dr. Rodd. "When the condition is that serious, the patient should really be referred to a physician, since in rare cases severe mouth ulcers can be a symptom of a bigger problem, such as Crohn's disease or Behcet's disease." Pharmacists can refer patients with persistent mouth sores to an oral pathologist. "These specialists are found through medical centers or dental schools," he said.

For milder cases (occasional lesions), treatment is focused on controlling discomfort and protecting the sores from irritation from food or routine oral hygiene. "The biggest problem is that these lesions hurt, and OTC products, while they don't actually heal, do a good job of providing pain relief," Dr. Rodd said.

Topical products containing benzocaine?such as Anbesol, Orabase, or Zilactin-B?often are recommended. Dr. Rodd recommends a gel formulation, because a gel provides a polymer membrane over the ulcer, helping to create a barrier and reduce pain. Other products on the market include Campho-Phenique, Carmex, Gly-Oxide, Kanka, and Tanac. Dr. Rodd cautions that patients with a history of hypersensitivity to benzocaine should not use benzocaine-containing products.

Products that release nascent oxygen also can be used to provide temporary relief but should not be used for more than 7 days. Saline rinses can provide some soothing relief to the area.
