How to Tell a Canker Sore from a Cold Sore

Aaron Chy, BSc General, PharmD Student

What’s that on your lip?

Chances are, you’ve experienced it before; you’re casually eating or talking when, suddenly, you notice a sharp pain somewhere inside your mouth. Feeling around with your tongue, you notice an odd bump that wasn’t there before, and a quick look in the mirror reveals a small, white bubble on the inside of your lip. Yikes. Where did it come from? Is it contagious? Is this herpes?

Take a deep breath, and slow down. Fortunately, it may not be what you think it is. The truth is, if you’ve ever experienced a scenario similar to the one above, these symptoms are more characteristic of a canker sore, which is actually very different from a cold sore.

Canker Sores

A canker sore, formally known as an aphthous ulcer, is something that occurs very commonly and often presents on the inside of the mouth. Canker sores typically present as:

• A small, raised bump on the inner lip or tongue
• White-gray in colour
• Painful to the touch, making it hard to eat or speak

The exact cause of canker sores is remains unknown, but they’re known to be a product of inflammation. They have been linked to stress and allergies, as well as nutritional issues and mouth injuries (like biting yourself). The good news is that, while painful, canker sores are non-infectious, and typically resolve on their own in about a week.¹

Fun little fact: women, individuals under 40, and individuals in the middle and upper-middle classes, for whatever reason, tend to develop canker sores more frequently.¹

Cold Sores

Cold sores are different from canker sores since they typically occur outside the mouth, though in some cases they can appear inside as well. They typically present as:¹

• One or more small, round lesions on the outside of the lip, almost like a pimple
• May or may not show scabbing
• May be painful, or itchy
• May be accompanied by mild chills, fever and other flu-like symptoms

Unlike canker sores, which have no infectious component, cold sores are caused by the Herpes Simplex Virus (HSV). Since cold sores are known to be caused by the same virus as genital herpes, they are often a topic of embarrassment and carry a shadow of stigma. That said, cold sores are not considered a sexually-transmitted disease, and they can happen to anyone, regardless of sexual activity. HSV is contagious through saliva, which means that when a cold sore is actively happening, there’s a greater risk of passing the virus on through kissing, or sharing drinks. Unfortunately, the virus sticks around life-long, but can be kept in check with certain medications.¹

In addition, if an individual has a history of cold sores, this does not mean they’re continually contagious. The risk of transmission is highest during the time a cold sore is active, as well as shortly before and after. The onset of a cold sore is typically signalled by a unique tingle that occurs around the mouth/lips a few hours before the outbreak. This is generally the cue to start being careful (avoid kissing and sharing drinks/eating utensils).

Some Lip Service

With canker sores, you can simply wait 7-10 days for the sore to heal itself. In the meantime, you can manage the pain with:¹

• Acetaminophen (Tylenol^©)
• Ibuprofen (Advil^©)
• Oral numbing creams/gels (lidocaine, benzocaine)

Cold sores generally last for about two weeks, but should be treated with anti-viral medications to speed up recovery, reduce pain, and reduce the chance of spread/other complications. There are over-the-counter topical products available (eg. Abreva^©), but the most effective options are prescription medications. Consult your healthcare provider about some of these medications if you’re concerned you may have a cold sore (this may not be a complete list, as available options may vary by region):

• Valacyclovir (Valtrex^©)
• Famciclovir (Famvir^©)
• Acyclovir (Zovirax^©)

These medications can be used preventatively as well. Individuals who have a history of cold-sores are often prescribed a supply of medications that are kept on-hand and can be taken pre-emptively if there are concerns that a cold sore is about to develop. Individuals who are familiar with their condition can often predict the onset of new sores based on the characteristic tingling and the presence of triggering factors, which include:¹

• Any form of stress
• Sun exposure (e.g. from the beach, or even ski hills)

We hope this helps clear up some confusion. Rest assured, these conditions are very common, don’t feel embarrassed to approach a care provider if you’re curious about what treatment is best for you. Also, don’t be afraid to ask for a private area to speak in if you’re uncomfortable discussing in public. As always, feel free to contact us at ask@orbishealth.ca with any questions, comments or concerns.

RESOURCES

1. RxTx