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What is a canker sore (aphthous ulcers) verses a cold sore (herpes simplex)?

Updated: Aug 24, 2022

You’ve heard that question from patients and friends many times and there are a variety of ways to answer it, but many of the answers are pretty much useless to the layperson and actually not that useful for a dentist or hygienist, since the question is usually a clinical question and not a causal or etiology question. The patient wants to know the difference they can recognize and understand when they have an oral ulcer.

I can summarize the clinical difference between aphthous and herpes in three words, location, location, location.

Aphthous ulcers only occurs inside the mouth and when they do occur, they only occur on unattached mucosa; inside the lips, on the cheeks or under the tongue.

Secondary Herpes attacks occur primarily out on the lip. Most of the time the attack starts with a tingly sensation, then a little blister and then a crusting ulcer. But secondary herpes attacks do occur inside the mouth and when they do, they only occur overlying hard tissue; the roof of the mouth and attached gingival mucosa. They usually occur as a cluster of small ulcers which enlarge slowly as the attack progresses.

So that is what I mean about location being a key distinguishing clinical characteristic.

Another distinction is that herpes attacks are constantly painful, especially if the patient thinks about it, (herpes is a neurotropic virus so it inflames the nerve causing constant pain). Aphthous ulcers are only painful when disturbed either physically with food or even water or, especially painful is acidic foods like orange juice.

Who knows these simple and meaningful clinical differences? You do! Who doesn’t know the difference between aphthous and herpes, patients, physicians, nurses, pharmacists and all the other people that patients tend to ask? So, it is us as oral healthcare specialists to be the ones to make the correct diagnosis.

Herpes and aphthous are, of course, two completely different and unrelated diseases. Plus, they are not the only ulcerative diseases that can occur in and around the oral cavity, but, as you know, a correct diagnosis is the key prerequisite to proper treatment of any disease.

The above, quickly evaluated clinical differences, which the patient can easily tell you over the phone, will get you to a correct diagnosis. Once you have the diagnosis, the proper treatment follows. Though, of course, the treatment for aphthous ulcers and oral herpes is relatively limited and is mostly a grin and bear it prognosis/treatment plan, but the patient appreciates knowing for sure what they have and that both types of ulcers are self-limiting.

If you are interested in the various treatments for aphthous or herpes, that is outlined in my Little Dental Drug Booklet. For aphthous, the treatment is mostly to cover it up or numb it or do both. The treatment for herpes is antivirals at the first tingling sign of the pending attack.

I hope you enjoyed that Dental Tidbit and found it informative. Check back for more Tidbits or, if you have a dental pharmacology or oral medicine question, please send it to me and I will get back to you personally, plus, perhaps create a Dental Tidbit for others that might have the same question but have not yet asked.

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