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Dr. Jeff Hersh: What causes a canker sore?

Dr. Jeff Hersh: What causes a canker sore?

Q: I have a small, white, painful sore under my tongue. I have had this several times before and it usually goes away after a week or so, but it seems to come back again. Is this a cold sore?

A: You should see your dentist or health care provider to be sure, but it sounds like you are describing a canker sore (aphthous ulcer).

Canker sores are ulcers that occur under the tongue, on the gums, inside the checks, by the back of the throat or on the soft palate (the roof of the mouth). They are very common, affecting up to 1 in 5 people in their lifetimes.

Canker sores are not the same as cold sores. Cold sores are due to a herpes simplex viral infection, and are typically outside the mouth on or around the lips. Cold sores are contagious, whereas canker sores are not.

The cause of canker sores is not known. There is a family predisposition; about a third of people who get them have a family history of them. Canker sores may be brought on by stress, trauma (including from overly hard tooth brushing, gum chewing, a cracked tooth, newly applied braces, dentures or other dental appliances), acidic foods (such as certain fruits and vegetables like lemons, limes, tomatoes, apples, pineapples, strawberries, many others) or spicy foods. Deficiencies of B12, zinc, folate or iron may be associated with canker sores. Finally, some diseases may increase the risk of developing canker sores including immune compromising diseases (HIV for example) and certain gastrointestinal conditions (such as celiac disease or inflammatory bowel diseases).

Simple canker sores are small (usually a quarter inch or less in diameter), painful, round/oval with a white/gray base, surrounded by a reddish area. They usually occur in people between the ages of 10 and 25, typically one at a time (although a couple are possible). They may come as much as three to four times a year for several years, and then less frequently or not at all.

Major canker sores are larger and deeper than simple canker sores, although still usually white/gray surrounded by a reddish area. They may be irregularly shaped, occur in larger numbers (in general, although they may occur as one or two ulcers), and typically take much longer to resolve than simple canker sores, up to six to eight weeks. Major canker sores are more likely to occur at a later age than simple ones, typically in people in their 30s or 40s.

Herpetiform canker sores start as many small ulcers that meld together to form one or more bigger ulcers. Despite the name, these are not associated with the herpes virus. Except for how they form, they are fairly similar to simple canker sores; they usually resolve in a couple of weeks.

Since canker sores typically resolve on their own, only symptomatic treatment is usually required. This may include an over-the-counter topical numbing agent (similar to medicines used for a baby’s teething pain), mouth rinsing (I sometimes recommend “magic mouth” which is a solution made of half liquid milk of magnesia and half liquid diphenhydramine which can be swished and swirled around the patient’s mouth for a minute or two and then spit out), ice (for example by holding ice chips in your mouth against the ulcer) or other treatments. For patients with a vitamin deficiency (and possibly in some people without a significant deficiency), vitamin supplements may be beneficial. For those with an associated medical condition, treatment of this condition may be indicated. In rare cases, usually for very deep, poorly healing, significantly symptomatic canker sores, cauterization may be utilized.

Although there is no way to completely prevent canker sores, for those that are predisposed to them avoiding triggers (as listed above) can be helpful. There are other conditions that may have some similarity to canker sores, so if you develop an oral ulcer that does not resolve within a week or two, that prevents you from drinking sufficient fluids, that is accompanied by fever or swollen glands, that is very large, or if you develop multiple oral ulcers, you should see your dentist or health care provider to have it checked out.

Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.

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