How to tell difference between cold sore and canker sore

These two ailments are commonly confused. Both canker sores and cold sores occur near the same location, share many of the same triggers such as stress, facial trauma, and hormonal changes and can be very painful. But, it is important to distinguish between the two conditions to ensure that you get the best treatment available.

Canker Sore

Cold Sore (Fever Blister)

Canker Sore

Cause: Not clearly defined. Can be triggered by stress, fatigue, hormones, or facial trauma.

Cold Sore (Fever Blister)

Cause: Herpes simplex virus (HSV). Outbreaks can be triggered by stress, fatigue, injury, or exposure to extreme conditions.

Canker Sore

Location: Inside the mouth and on the gums.

Cold Sore (Fever Blister)

Location: On or around the lips, mostly outside of the mouth.

Canker Sore

Appearance: Typically small open sores with white, yellow or gray center and bright red border. Can be single or in groups.

Cold Sore (Fever Blister)

Appearance: Red, fluid-filled blisters, typically in groups.

Canker Sore

Contagious? No.

Cold Sore (Fever Blister)

Contagious? Yes. Skin-to-skin contact with an active cold sore blister can spread the virus.

If you've ever had a sore on or near your mouth, you've likely thought to yourself: Is this a canker sore or a cold sore, and what's the difference? Here are three significant differences of a canker sore vs. cold sore to help you determine your next steps for treatment.

1. Appearance

The first way to differentiate a canker sore vs. cold sore is by appearance. As the Mayo Clinic explains, canker sores — also called aphthous ulcers — appear inside the mouth. They develop in soft tissues, such as in the cheeks, gums, under the tongue or on the tongue. Canker sores look like small white or yellow circles surrounded by a red border and may cause discomfort when you eat or drink.

Cold sores, on the other hand, usually appear on or around the lip, as the Mayo Clinic explains. A cold sore often looks like a cluster of blisters, and they can eventually burst, causing oozing and crusting.

2. Causes

Canker sores and cold sores have different underlying causes. According to the American Dental Association, the exact cause of canker sores is unknown. Experts speculate that they may happen as a result of immune issues, mouth trauma, bacteria or viruses.

Cold sores result directly from the herpes simplex virus (HSV-1), according to the Mayo Clinic. This virus is dormant until triggered, which is when you might experience a tingling or burning sensation in your mouth and the development of a sore. Several factors can trigger the recurrence of a cold sore:

• Stress
• Other viral infections
• Fatigue
• Exposure to sun or wind
• Hormonal changes
• Fever

3. Treatments

Both canker sores and cold sores usually heal on their own. Minor canker sores typically take a week or two to heal, according to the Mayo Clinic, while cold sores may take two to four weeks. Cold sores usually do not leave scars; however, major canker sores have the potential to cause scarring.

If your symptoms last longer than you'd like, you can also discuss treatment options with a medical or dental professional. For canker sores, if they are unusually large, clustered or painful, your doctor or dentist may suggest mouthrinses, topical ointments or oral medication.

Because cold sores are caused by HSV-1, the American Academy of Dermatology (AAD) suggests treating them with antiviral topical or oral medications. If you are experiencing discomfort, your doctor or dentist may also prescribe a pain-relief medication. In addition, the AAD strongly encourages the use of sunscreen during an outbreak, as sun exposure can affect the healing of the sore.

Another important note: Unlike canker sores, cold sores are contagious, according to the Mayo Clinic. Therefore, to prevent spreading the virus, you should not share utensils or any other items that touch the mouth.

The easiest way to tell the difference between a canker sore and a cold sore is by its location. If the sore is in your mouth, it's likely a canker sore. If it's outside the mouth, it's probably a cold sore. If you aren't sure — don't worry. See your doctor or dentist so that they can determine what it is and recommend the proper treatment.

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